These transponders are already used for many year. They inject them in pigs and cows to identify them. And some car manufacturers put the into the ignition keys as theft protections. Technology is not new. Perhaps it is already used for criminals? Somewhere I heard that in America criminals are sentenced to stay at home because the jails are overfilled. A sender is attached to their leg and the police is informed if he leaves his home. Perhaps a drug dealer may be more usefull if he moves free and has a transponder inside which he doesn't know about, that having him in jail. Here in Germany most department stores have big antennas at the doors which are normally used to detect thefts. Perhaps these antennas also recognize certain people. You can be sure even criminals go to department stores, undergrounds, or bus stations. Some hidden antennas and it's easy to be on their track. But it might be difficult to hide them on x-ray images... Brrr, disgusting idea... :-{ Hadmut