This is no longer available. Too bad, because it allowed a sweet native looking effect
there are a few things you need to do to show the user wallpaper
1 - set UIApplicationIsOpaque to false in the project plist
2 - In the app delegate load function
self.window.backgroundColor = [UIColor clearColor];
self.window.opaque = NO;
3 - set the UIViewController.view background color to [UIColor clearColor]
This works for us currently. If you try to do a screen capture or actually use the wallpaper it just returns solid black (so privacy concerns don't apply since you can't do anything with the wallpaper).