OpenCV (Open Computer Vision) combined with UDK (Unreal Development Kit):
UDK + OpenCV from Dimitrii Pokrovskii on Vimeo.
The game image is processed in real time through OpenCV (C++ library) using a HoughLine analysis which identifies high contrast straight lines. OpenCV returns the line information back to UDK as vectors. The vectors are overlaid the in game image via the HUD. This all takes less then 0.1 seconds.
This was a thought experiment investigating how to combine computer vision and real time rendering to create new game mechanics.
If you want to pursue this idea further I would recommend not using UDK. There isn't enough access to the core engine to make this streamlined (as i learned). Email me, I would be more then happy to share the UDK code.