1. A tracking device comprising: an on-board power source; a central processing unit; a cellular telephony transmitter and receiver; a speaker and a microphone; a bus system interconnecting electronic elements; and software or firmware executing at least periodically from a machine-readable physical medium providing a range of functions for the device; wherein the device maintains a sleep mode until activated by an internal timing function, once activated turns on the receiver and listens for radio signals, finding particular signals, consults memory associations with one or more of those signals, and determines to activate transmission only under certain preprogrammed conditions depended on signals found and identified.