A system (100) includes a wireless device (101) and at least one transponder (102). The wireless device (101) includes a memory (201) with an area (202) for storing coupling range profiles, a processor (203), a bus (210), a receiver (206), a transmitter (205), an alarm (208), a location module (209), a user interface (211), an antenna (212) for receiving transmitted location information, a power controller (204), an antenna (207) for transmitting and receiving, and a clock (213). The transponder includes a memory (301) with an area (302) for storing a unique transponder ID, a processor (303), a bus (308), power controller (304), a receiver (306), transmitter (305), and an antenna (307). The wireless device (101) compares current context information to a coupling range profile and, based on the results of the comparison, transmits to at least one transponder (102) at an appropriate power level. If the transponder (102) is within the predetermined range, it will transmit and the wireless device (101) will receive a response signal. If the current location context changes, the wireless device (101) will automatically affect a change in coupling distance to the transponder (102).