Starting October 2006 the US will issue all new passports using the same ISO 14443 RFID tag and Basic Access Control encryption scheme employed by the Dutch e-passports (and others) and adopted by the ICAO as global standards.

ENGADGET: Dutch RFID e-passport cracked -- US next?

Any curfew breaches or interference with the tag is reported to a control centre.

BBC: Serco and G4S face billing probe over electronic tagging

If a sensor detects a problem, the RFID tag transmits this to the control unit which can emit an (audible) alarm or shut off the water supply.

ENGADGET: RFID is in the toilet