DETROIT -- Your car stands little chance of being stolen, so long as you've got your cell phone handy. That's the premise behind a Bluetooth-based auto security system called Auto-Txt. The underlying technology was shown this week at the Telematics Detroit conference.

Auto-Txt works this way: Start with a Bluetooth-equipped cell phone and a car with a Bluetooth module from Ezurio, a London-based supplier of Bluetooth and WiFi modules. Add the Auto-Txt vehicle tracking, notification, and recovery service from RDM Ltd., of Coventry, England.

The car owner's cell phone is registered as belonging to that car, and when the car is started, Auto-Txt checks for the Bluetooth presence of one of the registered cell phones. If it's not present, the car is considered potentially stolen, even if the proper keys were used. The vehicle then can be tracked or remotely disabled.

RDM apparently has workarounds for people who forget their cell phones or let their phone's battery die. In other words, the car isn't automatically disabled just because the owner is a dolt.

So far Auto-txt is available only in Europe. Jaguar Cars and Land Rover have contracted to use the service in 2006.