1. A system for determining an activity of a user comprising: a hardware device comprising: at least one infrared imaging sensor configured to receive infrared radiation signals emanating from an object located within a predefined, three-dimensional personal activity space and not within a space outside of said personal activity space, wherein said at least one sensor is configured to detect object-defining thermal differentials in said 3-dimensional personal activity space; a memory in communication with the device, the memory adapted to store: object information relating to a plurality of potential object types with which the user may interact; and activity information relating to a plurality of potential activities the user may undertake with one or more of the potential object types; a processor in communication with the device and the memory, the processor configured to: determine a first position of the object in three-dimensional space at a first time, based on at least some of the radiation; determine a three-dimensional shape of the object, based on at least some of the radiation; determine an object type of the detected object from the plurality of potential object types stored in the memory, based on the determined shape of the object; and determine the activity of the user from the plurality of potential activities stored in the memory, based on the object type and the first position of the object.