Nothing, but I think I saw a plugin (or what that's called in emacs land) that uses it for syntax highlighting. I definitely know there are such plugins for vim and sublime. It seems to be pretty easy to interface with clang for such purposes.

There is also an auto-complete provider that uses clang for giving completion suggestions. I also think there might be a company-mode backend in the works, though I'm not sure about this one (company-mode is the "official" completion framework for emacs, while auto-complete is the unofficial but most widespread one).