Foursquares Swarm app is now available for iPhone and Android, letting you find nearby friends and check in to bars, restaurants, and other places. Foursquare announced Swarm two weeks ago as one-half of its new split personality — one app for finding friends and checking in, and another (launching later this summer) for finding great places to go nearby. Like Foursquare, Swarm lets you check in to show friends where you are, but it also uses passive location signals to show you which friends are nearby even when they havent checked in. With Swarm, Foursquare also took the opportunity to try out a few new ideas.