New iPhone app Sonar makes use of the foursquare application-program interface to tie in check-ins with users’ Facebook and Twitter connections, so users can determine if they are linked to other users at the same location or event.
foursquare platform evangelist Akshay Patil has more on Sonar in a post on the foursquare Blog:
Have you ever checked in somewhere, seen a few other people checked in, and wondered how you might be connected to them? Sonar, a new iPhone app, does that for you. It layers Facebook and Twitter connections atop your foursquare friends, so you can see who you know in common and how you’re linked. So the next time you’re at a crowded café or a conference, you can easily discover people nearby with whom you have plenty in common, and maybe even strike up a real life conversation.
We love ideas like Sonar; that’s why we made the location-related endpoints of our API available at high rate limits without specific end-user authentication, so all developers can use our venue database to easily add real-world location to their amazing apps. For more information and to get started, check out developer.foursquare.com.