Is there a proximity based lojack system that can be used for bicycles?

As of yet there's no commercially available GPS type tracking system for bikes. However not like an idea like that doesn't have merit. Some time back in I read about a bicycle theft ring getting busted by a GPS location device planted in a bike frame by the authorities. The high end mountain bike then was planted at a local community collage and quickly stolen by an unsuspecting thief. They tracked the bike's signal which lead them to a garage that had the remnants of at least 250 stolen bikes inside.