I think there is a huge opportunity in chatrroulette if we can just solve the "penis problem".
I've used chatroulette a few times over the past week and if you find someone "normal" to talk to it can be a lot of fun. That said, you spend most of your time "nexting" perverts.
I've been toying with eye-tracking using computer vision for assisting individuals who find themselves paralyzed after a car accident, stroke etc. But I'm not (yet) a CV expert, so I have a long road ahead of me. Part of my desire in this field is to have the computer boot and automatically detect the face and specific facial features from the webcam, with no calibration.
There is a lot of existing work in this area and it seems to me if we can detect a mouth on a face in a video stream we could use the same methods to detect someone jerking off.
I think the hardest part in the process would be finding an army of labelers that would put up with labeling the disturbing imagery. (Can you even submit this kind of material to mechanical turk? I'm not sure.)