_UICreateScreenUIImage() basically does the same thing as the well-known UIGetScreenImage(), except it is much, much faster. I haven't benchmarked it yet, but there is no noticeable lag - even on the 3rd gen iPad (UIGetScreenImage takes ~0.5 seconds on the same device).
It returns a standard UIImage that you can use however you like. Take note that you are responsible for releasing it yourself.
extern "C" UIImage* _UICreateScreenUIImage();