Sonar is riding a wave of social discovery apps that includes Banjo, Glancee and Highlight, but it isn't a newcomer. The New York based startup has made the rounds on iOS for the better part of a year, but today it's available in beta on Android to a handful of lucky readers.
Like others in the field, Sonar enables you to make meaningful connections with people around you -- people you wouldn't otherwise have known. It works by aggregating geolocation data across social networks and then creating relational correlations among individuals based on shared connections. So if you're having lunch and a friend of a friend walks in, you'll have the opportunity to connect with the person on the spot.
The field for social discovery apps is getting crowded quickly, but it seems that no one yet has gotten it quite right. Until then, we're likely to see other apps, and possibly new efforts from established geo players like Foursquare, before the industry crowns a clear winner.