1. Apparatus for verifying the presence of a particular human individual at a given location for a given period of time by repeatedly assessing a changeable visible identifying feature of said human individual, said apparatus comprising, in combination: (a) a computer database in which are stored a plurality of images of said visible identifying feature and other identification data of at least one registered human individual (“RHI”); (b) a first processor coupled to the database for accessing selected information from the database and for producing at least one prompt signal; (c) at least one first camera arranged (1) to view an identifying feature of a putative human individual (“PHI”), and (2) to repeatedly generate successive test images of said identifying feature of said PHI during said given period of time for transmission to said first processor; (d) a prompt producing device, for producing at least one prompt in response to said at least one prompt signal received from said first processor, for inducing at least one anatomic change in said identifying feature of said PHI; wherein said first processor is operative to: (1) generate said at least one prompt signal for transmission to said prompt producing device; (2) repeatedly compare each of said successive test images of said identifying feature of said PHI received from said at least one first camera, with said stored images of the identifying feature of said at least one RHI to repeatedly verify the identity of the PHI during said given period of time; thereby to repeatedly verify that the PHI is the same individual as one of said at least one RHIs during said given period of time, or to determine that the PHI is not the same individual as any one of said at least one RHI.