Danes tag kids with Bluetooth | The Register

Tivoli Gardens (Copenhagen) has introduced a Bluetooth surveillance system for parents with small children.
Parents buy a armlet for their kid and if they lose sight of him, they send a SMS requesting information on the particular tag. Then they receive a message indicating the location (down to 20 metres) of the child’s nearest Bluetooth receiver.

The Child Spotter Service combines Bluetooth wristbands developed by Bluetags and access points manufactured by Blip Systems.