reference will now be made in detail to a preferred embodiment of the message delivery system of the present invention . fig1 shows a synoptic of a possible embodiment of the system of the invention , installed in a house of a user 1 , where a wireless local network has been installed . the system includes a series of display devices — which in the preferred embodiment are also referred to as ‘ infospaces ’— connected to such network , and distributed along different rooms within the house . in the embodiment shown in fig1 such display devices are : a series of wall - mounted monitors 100 , 100 ′, distributed around the house , e . g . one wall mounted - monitor in each room ; a personal computer 101 , in one or more of the rooms ; an equipped tv - set 102 ; a mobile device 103 , ( e . g ., pda , cell phone or wrist watch ), which in the embodiment shown in fig1 also includes a motion sensor , e . g ., accelerometer ; and an “ electronic post - it ” 104 or mobile autonomous display . the wall - mounted monitors are capable of displaying paintings , photos or decorative pictures when there are no messages . these “ electronic post - its ” are flat mobile devices that can work without wired connections , have an autonomous energy supply , and that can be fixed on a metallic surface ( e . g ., by means of magnets ), or can be placed on tables or flat surfaces ( e . g ., by means of a removable support ), or can be hung at a vertical surface ( e . g ., by means of orifices in which nails and / or hooks are inserted ). as indicated , all of these display devices are connected to the wireless local network , and one of the display devices acts as a network server . a display device can be dynamically connected to another network , so it can transport information between different networks . in the case shown in fig2 , the leftmost wall - mounted monitor 100 has been assigned to work as a network server in this case , for which purpose it also has a wifi router and runs a server application in parallel . but the server could also be possibly implemented in any other device , for instance , in a laptop , be it working as a display device ( as it would be the case of a laptop , which includes a display ), or be it working as a network server with no additional monitoring functionalities ( as it would be the case of a “ processing box ” without display means ). a way of presenting information to the target user , either by : visual means , such as a display , like an lcd screen 10 , audio means , such as a loudspeaker , tactual means , such as a braille display , so that the message can be delivered to any target user , independently of he / she being deaf , blind or physically impaired ; an interaction mechanism or minimal entry of command , like a touch screen , a button or a key , a stylus or a mouse , an external entry of commands like a decoder for a remote control ; a processor ; input / output ports ; a real time clock ; a network connection ; and , supply means , like a plug to be connected externally or batteries . these display devices also include one or more software applications ( micro - programs )— which in the preferred embodiments are also referred to as ‘ infodgets ’— that display a message under different modalities in a window , and are composed of : a program or micro - program , the data of a message , and an activation condition and a satisfaction condition . a set of presence detectors 200 , 200 ′, which can be integrated in the wall - mounted monitors 100 , also distributed around different rooms in the house ; and a set of local environmental sensors 201 , 202 , 201 ′, 202 ′, e . g ., door , inundation , temperature . . . installed in several places around the house . these presence detectors can be any of the following : motion detectors , 200 ′ like the classical infrared detectors , but also camera - based motion detectors , sound detectors , passive infra - red detectors that detect body heat , rfid readers that detect a rfid pin worn by a person . . . all these sensors are also connected to the network , either directly or indirectly by means of the i / o ports of the closest display device . these display devices are programmed to execute infodgets , to capture information from sensors on the i / o ports or by means of the network , to compute a presence probability estimate in a neighbour area , to exchange with other display devices sensor states , software applications ( infodgets ), presence probability estimates , and in general , any type of data , to send commands to other devices and to execute commands received from other devices . in this example , “ presencedetector1 ” is a binary sensor , such as an infrared active detector . [ in this syntax used , the parentheses indicate a variable ( state of the detector )]. in this case the presence probability estimate is binary , 1 or 0 . in this case there are two binary presence detectors , and the presence probability estimate is an average of the two detectors , and so it can take the following values : 0 , ½ or 1 . in this case there are two analogue detectors which measure the levels of movement and of noise , but the presence probability estimate is binary , either 0 or 1 . the display devices ( infospaces ) of the system can have the following functionalities : i ) continuously monitor the local environment sensors and the presence detection sensors and compute the presence probability estimate , the activation condition and satisfaction condition of a set of applications ; ii ) transmit information about the environment and about the applications ( infodgets ) that are currently active to the other devices via the network ; iii ) launch applications when the local environment fulfils determined conditions ( see below ); iv ) display the message of the active application on its display at different locations , according to the commands sent by the applications themselves ; v ) transfer applications to other devices according to the commands sent by the applications and / or the location of the messages on the monitor ( e . g ., when they reached a transfer zone ); vi ) launch applications in response to the transfer commands sent by other display devices ; vii ) maintain a copy of applications that can be activated at any moment in response to determined conditions in the environment ; viii ) maintain a local copy of inactive applications ( called cemetery ) used to speed up the transfers , by using the local copy instead of transferring again the whole application ; ix ) store statistics and event information with a time stamp ( instant of occurrence ) until they are sent to the network server ; x ) execute the commands sent by the network server ( e . g ., for tests or for ending the execution of given infodgets ); xi ) periodically send statistics and event information to the network server in charge of collecting them . fig3 shows a typical layout of the display or screen 10 of a display device . it has four areas or zones : a start zone 11 , a stage zone 12 ( to display a message ), a backstage 13 ( when the infodget has no message to display ) and a transfer zone 14 ( when the infodget requires transfer to another display device ). the typical path of a message in a display is the following : from the start zone 11 to the stage zone 12 , where the size of the message is increased ( shown by arrow a ). then when the message is acknowledged , for example , by interaction of the target - user 1 , the message goes from the stage zone 12 to the backstage 13 , where the size is again decreased ( shown by arrow b ). when the message is reactivated due to some reason , the message is transferred from the backstage to the stage zone ( shown by arrow c ). and finally , when the current display device is no longer adequate , for example , because no movement is detected in the room where such display device is , the message is moved from the stage to transfer zone 14 , where again its size is decreased ( arrow d ). the local network is composed of a network server ( leftmost wall - mounted monitor 100 in fig2 ) and connections placed in each display device ( infospace ). the local network is used to : transmit the state of the environment of each infospace to the others ( transmission in broadcast mode ); transfer applications ( infodgets ) from one infospace to other infospaces ; collect information on traffic ( event log ); send commands to the infospaces in order to display and / or hide messages ; send sequences of commands to the infospaces in order to control them externally or to test the response to a series of changes in the environment ( test and simulation functions ). the network is also used to collect information from wireless sensors , and if applicable , it is also used to send commands to actuators . i ) establishing communication with all the infospaces of the system , i . e ., assigning them an identifier ( typically an ip address ), initializing the connection ( server side ), checking the status of the connected devices ; vi ) maintain statistics on traffic and actions of the user , so that it is possible to analyze both the behaviour of the system and the behaviour of the user , for instance , for automatic detection of abnormal user behaviour . once the system and its elements have been described , let us consider some examples of events taking place in the system . for instance , suppose that the entry door ( not shown ) of the house where the user resides has an ‘ entrydoor ’ sensor 200 monitored by wall - mounted monitor 100 , an external light sensor ‘ ls ’ placed outside the entry door ( not shown ) and that the wall - mounted monitor 100 contains a software application stored in its memory named entry door ’ ‘ ed ’. in this case , a possible expression for the activation condition is the following : ( entrydoor )& gt ;= 0 . 5 , implying that the message is activated when the entry door is open . or the activation condition can be also expressed as follows : ( entrydoor )& gt ;= 0 . 5 and ( ls_level )& lt ; 0 . 1 , wherein the message is activated when the entry door is open and there are no lights outside , i . e ., by night . so let &# 39 ; s suppose an ever more specific case of the latter , wherein the activation condition of ed becomes true when : ii ) light sensor ‘ ls ’ is below a pre - established threshold ( there is no light outside the entry door in the entry room , which only can happen at night ), and also iii ) the duration of activation of ed is shorter than some predefined threshold ( time out , in case the user 1 does not acknowledge the message through the interaction means of the display device ). suppose that the satisfaction condition for ed is that the presence probability estimate of the current display device ( in this case wall - mounted monitor 100 ) is above a predetermined threshold , as determined from the state of the presence detection sensors of said device , e . g ., light sensors , motion sensors , noise detectors passive infrared detectors . in this case , the satisfaction condition can be expressed as follows : ( presence_probability_estimate )& gt ;= 0 . 5 , showing a simple case of satisfaction condition : the display device is valid for displaying a message if presence is detected . the satisfaction condition is binary . another possible expression for the satisfaction condition is as follows : (( presence_probability_estimate )& gt ;= 0 . 5 )+ 0 . 5 *(( infospace )=“ kitchen ”) in this case the satisfaction condition is higher for the display device that is in the kitchen . [“( infospace )” stands for the identifier of the current display device ]. this satisfaction condition takes the following values : 1 . 5 ( kitchen , somebody here ); 1 ( elsewhere , somebody here ), 0 . 5 ( kitchen , nobody ) and 0 ( elsewhere , nobody ). it is also possible to express the satisfaction condition as follows : ( presence_probability_estimate )& gt ;= 0 . 5 and ( displaydurationseconds )& lt ; 30 . in this example , if nobody acknowledges the message for 30 seconds , the satisfaction condition becomes 0 and the message starts travelling across the other displays , even if there is somebody ( some presence has been detected around the current display device ). ( displaydurationseconds ) is a time - related variable . other time related variables are ( hour ), ( date ), etc . back to the specific example , wall - mounted monitor 100 is permanently polling ‘ door open ’ sensor 200 and light sensor ‘ ls ’, determining its presence probability estimate , and polling the activation condition of application ed . as soon as the entry door is open (‘ entrydoor sensor 200 is on ), and there is no light outside ( light sensor ‘ ls ’ below its pre - established threshold ), the activation condition of ed becomes true , and wall - mounted monitor 100 launches application ed . then , wall - mounted monitor 100 periodically executes application ed , in alternation with other active applications and with its main loop : sensor polling , network polling , evaluation of activation conditions , etc . . . . application ed , when executed periodically , determines its own position on the monitor and displays its associated message . this message moves from the start zone to the stage zone , where it is displayed in full size . meanwhile , ed may produce alert signals ( e . g ., sounds ) if wall - mounted monitor 100 is configured in this way . meanwhile , in its main loop , wall - mounted monitor 100 evaluates the satisfaction condition of ed , i . e ., if there is presence detected by the current display device , which is wall - mounted monitor 100 . when the satisfaction condition of ed is below some threshold , wall - mounted monitor 100 examines the satisfaction condition for all the other display devices : wall - mounted monitors 100 ′ in the contiguous room , a personal computer 101 , equipped tv - set 102 , mobile device 103 and “ electronic post - it ” 104 in the case shown in fig2 . wall - mounted monitor 100 has this information related to the satisfaction condition for the other display devices , since the display devices of the system are constantly broadcasting their satisfaction condition , the values of the sensors that they monitor , including their presence sensors , and a copy is locally stored to have access to that information . wall - mounted monitor 100 detects that the satisfaction condition of application ed , for the wall - mounted monitor 100 ′ ( in the contiguous room ) is over the pre - established threshold , since motion sensor 200 ′ has detected movement in that room : as shown in fig2 , target user 1 is actually in the room where wall - mounted monitor 100 ′ is . then , wall - mounted monitor 100 transfers active application ed to wall - mounted monitor 100 ′ in the next room . wall - mounted monitor 100 ′ now monitors application ed ( activation condition and satisfaction condition ) on the basis of the information of ‘ entrydoor sensor 200 and of light sensor ‘ ls ’ transmitted by wall - mounted monitor 100 . ed displays its message , e . g . ‘ shut main door ’, on the display of wall - mounted monitor 100 ′, which the target - user can actually see . the message of ed remains displayed ( wherever it is , in the display of wall - mounted monitor 100 ′) until any of the following occurs : a ) user 1 acknowledges the message by means of an interaction with ed . b ) ed has been displayed for the duration determined by its activation condition ( time out without any interaction from the user ). c ) the user closes the entry door — either directly or by means of some actuator which can be remotely activated to shut the door — thus the activation condition of ed becomes false . in any of the above cases a ), b ) or c ), ed is considered inactive . the message of ed moves towards the backstage zone where it remains visible ( with small size and grey tones ). while in the backstage , the message of ed can be displayed again in full size by means of an interaction from the user . as soon as the interaction ceases , the message returns to the backstage . the message of ed remains in the backstage until it is pushed out of the monitor by some newer message that requires its place in the backstage . at this moment , application ed effectively ends . simultaneously , as soon as ed is considered inactive , wall - mounted monitor 100 broadcasts a command that cause ed to become inactive so that the message of ed is processed in the same way in any display device where it may have been visible . now , let us suppose that mobile device 103 contains an application pills ‘ p ’ in charge of reminding the user to take his / her pills at determined hour , e . g ., 8 : 00 am ( clock - based event ). in this case , the activation condition of p is true when : ii ) the duration of activation of p is shorter than some threshold ( time out , in case the user does not acknowledge the message ). mobile device 103 permanently polls the activation condition of application p , and at 8 : 00 am , p is launched . the lifecycle of p is similar to that of the application ed of the former example , except that p ends only in two ways , i . e ., the user acknowledges the message or the ‘ time out ’ defined in the activation condition of p is exceeded . considering another possible case , let us suppose that the personal computer 101 ( used as a display device ) also runs in parallel an application that gets daily weather reports from internet in text format and detects the presence of keyword “ rain ” ( external event ). this application interacts with the display software by emulating a rain sensor ‘ rs ’, e . g ., by writing the probability of rain in a file that is constantly monitored in the display of the personal computer and read in case of modification . on this personal computer , there is an application called rain ‘ r ’ that displays a message ( e . g ., it will be raining today , don &# 39 ; t forget your umbrella ). the activation condition of r is true when : ii ) the duration of activation of p is shorter than some threshold ( time out , in case the user does not acknowledge the message ), and iii ) the last time application r was activated is the previous day ( so that the message is displayed at most once per day ). the weather application continuously enters the probability of rain , the personal computer continuously monitors rs , and whenever the probability of rain is above the specific threshold , the message of r is displayed . the lifecycle of r is similar to that of the application p of the former example , except that r can at most be displayed once a day . as indicated before ( fig3 ), a message is born in the start zone of the display , and its software application ( infodget ) continuously determines its target . i . e ., a location on the display that depends on its internal state : message to be displayed , transfer to another infospace required , no message to display . the size of the windows that present the messages is automatically determined by the infospace . the infospace may change the size of the window according to its location on the display . the images and animation that compose a message are resized accordingly . for instance , messages may get larger when they are close to the stage zone , and smaller when they are close to the backstage . this increases the readability of active infodgets and allows to maintain more infodgets visible at the same time . infodgets move their messages towards the target location in the display by means of a pseudo - random algorithm . the infodget examines periodically a series of possible moves , typically of a few pixels , and determines the best one according to predefined evaluation functions and to a random decision biased towards the locations that have the highest evaluation functions , for instance , an algorithm based on the boltzmann &# 39 ; s probability distribution ( mac keown , k . p . “ stochastic simulation in physics ”. springer , 1997 ). the positions where there would be collision , i . e ., an overlap between the infodget and other infodgets or graphical components , are not considered . infospaces periodically evaluate the satisfaction condition of their infodgets . this expression returns a value that may change according to the state of the sensors monitored by the infospace , including its presence detectors , to timing information and to current infospace . for instance ( and as shown in the previous examples ), said satisfaction condition has a low value when no presence is detected by the infospace , and for specific infodgets related to kitchen devices , a higher value to the satisfaction condition is given for an infospace placed in the kitchen , than for an infospace placed in a bedroom . when the satisfaction condition is below some specific or predetermined threshold for some infodget , the infospace evaluates the satisfaction condition of this infodget for other infospaces , on the basis of the information transmitted by said infospaces . when the satisfaction condition is sufficiently high ( above another threshold ) in another infospace , the infospace changes the internal state of the infodget to request a transfer , and the infodget moves towards the transfer zone and waits . infospaces periodically examine their active applications ( infodgets ) and transfer to other infospaces those that are in determined locations of the monitor ( e . g ., the transfer zone ). the transfer of an infodget requires a complete communication between the source and target infospaces ( full handshake ). only when the transfer is successfully completed is the infodget deleted in the source infospace . when the target infospace has an updated copy of the infodget in its memory means , the transfer only sends a command that will activate the infodget from the local copy ( the files that compose the infodget are not transferred ). otherwise the source infospace transfers these files . in this case , the first visible form of the message , static image and / or animation may be transferred first so that it is displayed in the target infospace while the remainder of the infodget is completely transferred . there may be several copies of the same infodgets within the network , for instance , in case of failure of the transfer mechanism , or in case the same infodget is simultaneously activated in two different infospaces . to handle this situation , the infospaces continuously broadcast the list of their active infodgets , and the server sends a command to end the execution of the redundant copies that are detected . a certain amount of redundancy may be accepted , i . e ., the same infodget may be simultaneously active in different infospaces . these infospaces can be determined for instance as those for which the satisfaction condition of the infodget is above some threshold . the execution of all the copies ends when some infospace broadcasts a command to the effect of hiding the infodget . there may also be undesired copies of the same infodget on different infospaces , for instance , in case of failure of the transfer mechanism . to handle this situation , the infospaces periodically send the list of their active infodgets to the server , the server detects undesired copies by comparing these lists with the commands that were previously sent , and the server sends a command to end the execution of the undesired copies . each infospace monitors in real time the activation condition of its infodgets , and when the condition becomes false , the state and the target of infodget changes , and the infodget typically goes towards the backstage and remains there . in this state , any collision with another infodget makes the infodget disappear . any interaction from the user reactivates the infodget and it goes back to the stage ( see below ). in the preferred embodiment , mere is a single mechanism to interact with an infodget . for instance , this may be done by placing a finger on the infodget on a touch screen . under the effect of the interaction , the infodget undergoes a cyclic sequence of changes at a relatively slow pace . there is one state for each form of presentation of the information , e . g ., animation , static image , written text , spoken text or video . one state is the acknowledged state , in which the infodget stops moving or goes to the backstage . fig4 shows the typical sequence of states of an infodget under the effect of consecutive interactions . from left to right : normal active state 15 ( animation or static image ), written text mode 16 ( the text is displayed if there is no interaction within a delay e . g ., 2 s . ), spoken text mode 17 ( the text is read if there is no interaction within a delay , e . g ., 2 s . ), video 18 ( it starts if there is no interaction within a delay , e . g ., 2 s . ), and acknowledged 19 ( the infodget left in this state goes to the backstage ). the interaction can be done by touching the infodget on a touch screen , with the finger and / or by means of a stylus . or it can be done remotely , for instance , by means of speech or sound commands . the interaction can also be carried out by means of a key press on a remote control device , or by means of a movement done with the remote control device . it is also possible to drag the infodgets to desired zones of the display . for instance , an infodget can be dragged to the backstage to minimize its dimension and stop any animation or from the backstage to the stage , in order to display the message again with a large size . as shown in fig5 , first of , each display device polls the network to which it is connected to get sensor states , presence probability estimates and commands , and determine its active messages ( 501 ). also , other display devices are polled so as to receive messages from said display devices and make those messages received active ( 502 ). also , each display device constantly polls the presence detection sensors to which each display device is connected ( 503 ) and with the sensor state provided by such presence detection sensors the presence probability estimate is computed ( 504 ). then each display device polls its environmental sensors ( 505 ) and the activation condition is computed ( 506 ) and so is the satisfaction condition ( 507 ), determining , respectively , the active messages and which messages have to be transferred . according to the user &# 39 ; s commands — which are also polled by the display device —, the state and position of each message is determined ( 508 ). for those messages that are visible their state is computed and their target zone and position in the display device is determined ( 509 ). then the active messages are displayed ( 510 ) and those messages that are in the transfer zone are transferred to other display devices ( 511 ). this loop is repeated in each display device on the system . in the flowchart shown in fig6 the activation of a message is shown . activation of a message can come from an external command ( 600 ) when a command “ display ” is received from the network ( 601 ). it is then verified if there is a message already displayed on the current display device or not ( 622 ). activation can also take place when a message is transferred from another display device ( 610 ), and so a message from another monitor is received ( 611 ). it is also possible that a message is activated by the current display device ( 620 ), and so the activation condition is computed ( 621 ), and it is checked whether the activation condition for that message is valid or not (( 622 ). then the state of the message becomes ‘ active ’ and the target zone for that message becomes the stage zone ( 630 ) and the active message is displayed in the start zone of the display device ( 640 ). the flowchart of fig7 shows the termination of a message , either as ended by an external command ( 700 ) or by the current display device itself ( 710 ). ending of a message can be the result of a command “ remove ” received from the network ( 701 ), or deactivated by the current display device when the activation condition is computed ( 711 ), it is checked that the activation condition for that message is no longer valid ( 712 ), and a “ remove ” command is sent to the other devices ( 713 ). it is then checked if there is a visible message in the current device ( 720 ), in which case , the state of the message becomes ‘ inactive ’ and the target zone for that message becomes the backstage zone ( 730 ) and the active message is randomly moved towards the backstage zone ( 740 ) of the display device . it is then checked if the message is in the backstage ( 750 ), and in the affirmative , if there is collision with other messages ( 760 ). then , the message is removed from the display device ( 770 ). the flowchart of fig8 shows the transfer of a message , which occurs in the current display device when the satisfaction condition is computed ( 800 ), and it is checked that the satisfaction condition for that message is no longer true ( 801 ). it is then computed the satisfaction condition for other devices ( 802 ). it is then checked if a destination display device is found ( 803 ), and in the affirmative the state of the message becomes ‘ to be transferred ’ and the target zone for that message becomes the transfer zone ( 804 ). the message is randomly moved towards or around the transfer zone of the display device ( 805 ). it is then checked if the message is in the transfer zone ( 806 ), and in the affirmative , a transfer request is send . in case it is accepted ,( 807 ), the message is transferred ( 808 ). fig9 shows the typical movement of a message in a display device when its satisfaction condition is over a pre - established threshold . the message appears in the start zone ( 900 ) in small size , and it then moves randomly towards the stage zone ( 901 ), until the message is displayed in the stage zone in large size ( 902 ). then a user acknowledges the message ( 903 ) and the message starts moving randomly towards the backstage ( 904 ), where it is displayed in small size ( 905 ) and then the message disappears when there is a collision ( 906 ). fig1 shows the typical movement of a message in a display device when its satisfaction condition is over a pre - established threshold , the message appears in the start zone ( 1000 ) in small size , and it then moves randomly towards the transfer zone ( 1001 ), until the message is displayed in the transfer zone , also in small size ( 1002 ). then the message is transferred to another display device ( 1003 ) and then the message disappears ( 1004 ). the system allows to keep track of statistics on the system and the user . periodically , infospaces send statistics and history of events to the network server that subsumes them . these statistics can be used to detect failures in the functioning of the system , to optimize the configuration by detecting for instance the infospaces that are seldom used and replacing them elsewhere , by detecting the most frequent failure . the system can establish standard patterns of user behaviour , patterns of interaction with the system and / or patterns of activity determined by means of the state of the sensors , i . e ., presence in determined rooms at determined times . these patterns are kept local so that there is no violation of privacy . this way abnormal patterns of behaviour can be detected and an alarm can be sent to a remote monitoring central , so that it is possible to determine ( e . g ., by means of a phone call ) whether the user suffered an accident . the application of the system of the invention is typically domestic , but the system can also be deployed in an enterprise or a public system , and in general it can be used in any situation where information must be displayed in a way that catches attention and allows fast and easy understanding . the system is particularly designed for persons that are unfamiliar with — or reluctant to use — technology but it can be useful for anybody , according to the principles of design - for - all . it is to be understood that the above disclosure is an exemplification of the principles of the invention and does not limit the invention to the illustrated embodiments .