Joel Mathis on Ban.jo:
The app lets you plug into five different social networks: Facebook, Twitter, Foursquare, Instagram, or Google+. If one of your friends on those networks checks in or updates a geotagged status, Ban.jo alerts you if that activity is taking place nearby. The idea, according to Ban.jo’s developers, is to eliminate those times when you and your friends are within shouting distance of each other but might not know it.
Interesting concept. If I was more into the location-based stuff I would be all over this, because seeing it all in one place makes it so much more useful.