Foursquare has just released version 1.3 for their iPhone app, which now notifies you with a buzz when friends are nearby, via push notification. Foursquare allows you to check-in at different locations, and lets your friends know where you are (this also includes optional Twitter pinging.)  What makes this app stand out is the badges system. This system awards you for your activity, whether is checking in to a new place or returning to it for the 100th time.  Competitive souls can find subtle amusement by attempting to dethrone majors for locations – people that have been to a specific location many times.  If you haven’t tried out Foursquare yet, I highly recommend it.