Useful Networks, the American company behind Sniff, promised that only consumers who gave their permission could be electronically tracked by the service, which operates across all mobile carriers. Users can specify who can and can not sniff them, or whether they are open to be sniffed by anyone on the network. The company plans to charge users about 75p for each location “sniff”, with the results for mobile customers sent by return text. It will be the first Facebook application to apply premium charges to customers’ mobile bills. The heaviest users in Sweden are wireless-connected members of the social networking site, who have integrated the application into their personal profile page.

Useful Networks, owned by the American giant Liberty Media, hopes to introduce “sniffing” in Britain this month.