Epic has been working secretly on porting their popular Unreal Engine 3 to iPhone, and they are almost finished now.
The company's VP Mark Rein has shown a demo running the engine on iPhone to Anandtech's Anand Lal Shimpi. The engine currently works on iPhone 3GS, but not on its iPhone 2G and iPhone 3G predecessors since it requires OpenGL ES 2.0.
The engine also works on "another mobile platform entirely" that will be revealed at CES 2010 in January.
The iPhone Unreal Engine will be available to licensees sometime "in the near future", but Epic has no intentions to develop any iPhone games on its own.