IOS-PagePeel-Example is a project mainly written in Objective-C, it's free.
Example Xcode project that shows how to replicate the cool iOS page peel effect. Detailed in a blog post here: http://skookum.com/blog/ios-peeling-effect/
Skookum Digital Works http://skookum.com
Example project showing how to clear the interface using a page peel.
Video here: http://vimeo.com/25715609
Blog post here: http://skookum.com/blog/ios-peeling-effect/