Radio Frequence IDentification (RFID) is a not-so-new but recently acclaimed technology for, basically, tracking stuff. It involves tiny computer chips that can send a signal to a "reader". The RFID chips are small enough that they can be easily placed/implanted on/in almost anything one would want to track: a can of peas, a palet of dry goods, a child.
A study was done using RFID for the tracking a small group of chilluns to, ostensibly, keep them safe by tracking where they are or aren't.
Among other things, here's one discovery worth noting (see quote below). Remember this when you hear politicians of the future recommending measures to implant these in children as standard issue.
Link: RFID in Japan: Lessons learned: RFID Kids Tracking.
"There were 53 cases of emergency alarms, however, all of them were false alarms. Because of frequent false alarms, the volunteers eventually got less serious about running out there to help."