We can't think of many better ways to spend £3.60 a month than a new car-security system from Japan that uses a mobile-phone network to covertly track your vehicle should it be stolen.

Kato Denki's Stealth Tracking System relies on a 31g box that can be hidden anywhere inside a car to relay its position back to base through a mobile network owned by Wilcom, one of Japan's data-network specialists.

Triangulation approach

The device, which is the size of a large matchbox at 35 x 58 x 14mm, has an internal battery good for over ten days even if the engine is switched off and no longer charging it.

Standard triangulation techniques using the nearest available mobile masts can pinpoint the location of the device down to 10m, resulting in a postal address of the car's location.

Underground, overground

Kato Denki's monthly fee then allows subscribers to query a central server from a phone or PC when their car isn't where they left it. Unlike GPS, the Wilcom network provides coverage in typical hiding places – indoor car parks or underground lock-ups.

Optional services include a warning email when the car leaves a designated area and the ability to track the entire route a vehicle takes as its new 'owner' goes on a cross-country road trip.