Just been reading about Foursquare.  At its core, Foursquare is a location-based social network, but at the same time, it is also a nightlife game where users get extra points for being the first to visit a new place, going out every night of the week, and for adding new information about clubs and restaurants.

From within the app, you can update your location, send shouts to your friends, track your 'achievements,' and keep a to-do list that is shared with your friends. You can also add additional information about your favorite food or beer to your favorite hangouts.

Foursquare draws from a list of known restaurants, bars, and nightclubs. The iPhone app also integrates reviews from Yelp and Google Maps. The app currently features a database for 12 of the larger metropolitan areas in the U.S.  It will be interesting to see if they plan on international expansion.

Foursquare is a very cool application, and unlike other location-aware apps, it adds a competitive element to the interaction, as it rewards you for checking in whenever you arrive at a new location. This solves a major problem that has held back a lot of similar apps like Loopt or Brightkite in the past: users simply didn't have enough of an incentive to open up the app and check in every time they arrived somewhere new. With Foursquare, checking in, however, becomes the thing to do.

http://foursquare.com/