Useful Networks is launching its location-based systems tool Social Network Integrated Friend Finder, or sniff, for short, in the UK next month, on three of the country’s four major networks, as yet undisclosed. Of course, the service that lets people locate their friends on their mobile phone or from Facebook is all permission-based Useful Networks says, and is apparently “wildly popular” in Sweden where 80,000 users have signed up since it launched two years ago. To use the service, a person sends an SMS, and sniff returns a detailed map view of the friend’s location. Users are charged on a per “sniff” basis, which in the UK will cost £0.50 ($1.00).

But not everyone is happy with the service. The Times.co.uk trying to whip up a big brother frenzy around sniff and warns the tool could be used to expose errant husbands and employees “enjoying a long lunch or a secret liaison.” Neither of these complaints has much of a leg to stand on, but they do show how carefully location-based services need to proceed, as they tread the fine line of being perceived as a nuisance rather than as a tool (release).