Normally we'd give a brand new site a break for not immediately having an API. When it comes to the rabidly popular FourSquare, which launched in March, developers have been clamoring to build on top of the service. So, today's launch of the FourSquare API (our FourSquare API profile) is bound to be met with extreme enthusiasm.
In truth, the API has been out there since at least May, in use by a select few developers. That means that there are already a number of great examples in the app gallery.
FourSquare's service lets users within its cities "check in" to let their friends know where they are. There are a number of other services, such as BrightKite (our BrightKite API profile) and Shizzow (our Shizzow API profile), that have similar features. However, FourSquare made sharing locations a game. The service awards points, mayorship and badges to its users. With this, and unveiling its iPhone app at the popular SXSW conference, FourSquare took off.
The opening of the data is likely to be important for Foursquare in the long run. Foursquare is getting traction with users putting information into its system, but a real explosion could come if third-party developers start making some great apps on top of the service. Obviously, we've seen that type of community swarm around and feed services like Twitter.
The API provides access to the same functions that make the FourSquare mobile apps run. In addition, you can access a user's checkin history. Developer Andrew Mager details how to write a FourSquare app using OAuth and PHP.