The player has two Transceivers , both set on a certain frequency.
The player uses duck-tape or rope to keep Transceiver 1 in an always-on position.
The player plants Transceiver 1 at a certain location; ex: the door of his favorite police station.
The player can now move within the 5km range of Transceiver 1 and still keep an "eye" on the location, listening to the noise coming from Transceiver 2.