Japan's Tokyu Security has this PASMO Card going on for a long time, but the sevices included on the card have expended to unimaginable dimensions. Starting out as a card that allowed you to pay for your bus or train ticket (using RFID technology), this card has graduated to various sectors, like keeping a tab on your kids, retail point programs, coin locker keys, apartment access etc. from all the services offered I root for the child safety service. With this system, busy parents can keep a track of their kids. When the child uses the PASMO to check-in at school, enter/leave a train station, or arrive back at home, the parent is notified via mobile or PC. The system does not use GPS tracking as with kid-friendly mobile phones. The flipside to this technology is that your privacy takes a beating. Since companies can provide building access, employers will be able to keep a tab on the late arrivals plus will be able to counter check if that "late train" was really late! Source