BulgarianPride said:
GPS chips do not transmits, so it would be useless unless you also get the inhead navigation with imaps.
Skashion, you make good points, but they can easily be worked around.
1.) If tracking system is taken out of the body, it transmits an alarm. Detection of out of body can be done many ways. Drop of temperature, lack of heartbeat, gain/drop of humidity, pressure etc.
2.) and 3.) both are around not receiving the data send by the system. In that case, if a signal is not received in x mins raise an alarm with the last know position.
But anways implanting someone with a full blown GPS + some kind of transmitter system that allows the ranges required to be effect is a bit far from reach. It will not be effecting enough to be worth it.
GPS receivers don't but a GPS receiver would be as useful as a chocolate teapot for locating someone. To locate someone you need to be able to transmit a signal of some sort, it needn't be a GPS signal obviously, but the GPS coordinates would have to be transmitted in some way whether by phone network, WiFi, or 3G/4G. Having a chip where the kidnap victim knows their position but no-one else does is pretty damn pointless. Make no mistake that any device constantly sending GPS coordinates is going to very very power hungry unless it's RFID technology which would depend on it being absolutely ubiquitous.
and the problem of batteries running flat? Chips failing? Or even people stopping in one place too long so one position is continually broadcast giving rise to suspicion that something has gone wrong? There's going be a hell of a lot of false alarms.