When Apple unveiled iOS 6 during their WWDC 2012 keynote two weeks ago, they showed of a whole slew of new features. One of the most noteworthy, of course, was the all-new Maps app. The new Maps, done largely in-house by Apple, has includes a 3D Flyover mode and Siri-integrated turn-by-turn navigation. Those features alone are pretty impressive. One new Maps feature that Apple apparently didn’t mention, though, is Yelp integration.

According to a report this morning from Bloomberg, Apple’s new Maps app will include support for Yelp check-ins. Yelp already has a ridiculously handy iOS app that lets you find businesses, read and write reviews, and check in (a la Foursquare or Facebook or, well, just about any other social app these days). It’s not clear how many of Yelp’s features will be integrated into iOS Maps, but references to – and screenshots of – the check-in feature have been found in the iOS 6 software development kit (SDK) released by Apple following the keynote.

While integrating a check-in feature with Maps is a brilliant idea, the choice of Yelp seems an odd one. After all, another iOS 6 feature unveiled during the keynote was Facebook integration. Facebook, as you probably know, has its own check-in feature. That raises a very interesting question: why does iOS Maps integrate Yelp check-ins rather than Facebook check-ins? What about Foursquare, which is much more popular as a check-in service than Yelp?

Of course, it could be that iOS 6 Maps will have integration with other check-in services, and the references have not been found in the SDK yet. Or there could be some special deal between Apple and Yelp. There are three months (roughly) until the launch of iOS 6 and the new iPhone (probably). A lot can happen in that time, so for the moment we’ll just have to wait and see.