The location-based applications Foursquare and Gowalla--which reward users with points for "checking in" at different places--are all the rage in some social groups. But many other people balk at sharing their precise location and struggle to see the point of doing so. A new location-based application for mobile phones called face2face hopes to attract new types of users by offering more filtered, useful information and providing more privacy controls.

"Location is more a platform than it is a particular service," says Hameed Khan, CEO and lead developer of face2face. In other words, simply sharing location information isn't enough--it also needs to be incorporated into a useful application. His application doesn't require people to sign up to a new social network in order to use it. Instead, users can tap into their connections on Facebook, LinkedIn, MySpace, and Twitter--then see if any of their connections are nearby.

Unlike some services, which bombard users with the location of everyone in their social network, face2face only notifies users when a contact is nearby, and it does not give out that contact's exact location. This is a subtle difference, but an important one, according to Khan. "We want to look just at what's within walking distance, so oversharing doesn't ruin it," he says.

The application also comes with privacy settings that let users decide if they want to be invisible to others, and who they want to share their information with. Once users know they're near each other, the application lets them communicate, by text, phone, or messages on a social networking site.

Khan says users need a good reason to share their location information, and developers need to assure users that their location will only be shown to people they trust, and that this will be done in a way they can understand and control. Khan adds that social and location information can also make advertising more relevant. For example, in the future, instead of simply offering coupons to nearby coffee shops, his app may offer coupons to a coffee shop where a friend is already sitting.

But some say proximity-based services could make targeted advertising feel more invasive. "We're gallivanting into finally commercializing one of the last parts of life that isn't filled with ads: friendship and hanging out," says Michael Coté, an IT industry analyst with the research firm RedMonk.

Others, notably in the music industry, offer location-based applications that are more clearly useful. An early example was an iPhone app for the band Nine Inch Nails that filtered posts from users based on proximity. Fans at the same show could use the application to communicate with each other and the band. Rob Sheridan, the band's creative director, says: "It was perfect for us as a band on tour, because we have events where our fans gather together in close proximity, and I've found that events really are the best use for this type of thing."