Patent ID: 7652573

Claim:
A system for monitoring the presence or absence of objects, the system comprising: respective transmitters on the objects to be monitored for transmitting respective object signals specific to respective ones of the objects or to the transmitters; a GPS-equipped mobile telephone having a receiver for defining with the transmitters an observation areas in which signals outputted by the transmitters can be received by the receiver and outside of which signals outputted by the transmitters cannot be received by the receiver and for thereby receiving signals including the a one of the object signals only when the respective transmitter is inside the observation area; analysis means in the telephone and coupled with the receiver for, based on the signals received by the receiver, generating output signals indicating the presence or absence of the objects and their transmitters in the observation area, for determining when objects equipped with the transmitters enter the observation area, and for determining when one of the objects leaves the observation area and generating a data set indicating when the object left the respective observation area and the GPS location of the receiver when the object left the respective observation area; and an output device in the telephone for the output of the presence or absence output signal via acoustic, optical or haptic means.