London, June 3: A mobile phone tracking device which allows friends and family to find out where you are is being launched in Britain.

The technology delivers a map to the inquirer’s mobile phone, giving the location to the nearest 100 metres. But those behind the idea insisted that such a service can only work if the person being sought gives permission to be found.

And if someone has already agreed to be tracked, they have then option to be made “invisible” for as long as they want.

Users will be able to register on the Social Network Integrated Friend Finder via social networking sites Facebook, Bebo and MySpace, and each searching text will cost 50 pence. The service provider, American-based company Useful Networks, hopes hundreds of thousands of people will sign up.