Last December, mobile data swapping startup Bump opened up its iPhone API in a small, private beta. Today, they’re opening the floodgates to everyone. Developers who implement Bump’s API can use it to transfer data between two nearby phones simply by asking users to tap their devices together – a feat that’s still remarkably difficult on most smart phones.

To kickstart its API launch, Bump held a contest that invited developers to work the API into their iPhone applications. You can see a gallery of the winners here. The winning apps include CheckOut, which lets you share gift cards with friends by tapping your phones together; CloudNote, which lets you swap digital Post-It notes; and SocialFuse, which allows you to connect on Twitter and LinkedIn with someone (again, by tapping your phones together). Be sure to check out the gallery page for a half dozen runners-up to get more ideas of what the API can do.