The first Wi-Fi positioning system (WPS) which uses existing hotspots to triangulate locations has gone live.

WPS can work out the location of a Wi-Fi device to within 20-40 metres by comparing signals from a reference database of 1.5 million private and public access points.

So far the system only covers 25 US cities but Skyhook Wireless, which designed the technology, hopes to expand its reach.

"The opportunity is huge," said Craig Mathias, a principal with the wireless and mobile advisory firm Farpoint Group.

"We see wide-area positioning services like WPS as key to future mobile commerce, location-based services, tracking, mapping public safety, and many other applications."

The system is already being used by CyberAngel Security Solutions to track stolen hardware. If the correct log-in procedure is not followed, the device is configured to send out a silent alarm via Wi-Fi.

The Skyhook system then checks the longitude and latitude of the stolen device before sending this data to CyberAngel which co-ordinates recovery with local law enforcement officials.

The system works best in dense urban environments where the multitude of access points makes triangulation easier. The location calculation takes less than a second and does not need line of sight, as with GPS.

The software works with Windows XP and Windows Mobile, and a Palm version is due out in the summer.