A digital girl would be fun. Maybe you could create a simple game were the girls thank you in different ways. For example you rescue the princess and get a blow job.
I'm not sure how well a real game would work out. It would probably be a terrible piece of rushed programming pushed out the door to capitalize on the gimmick. However, a sex simulator that would act like a virtual webcam with actions programmed to utilize the realtouch would be a pretty great thing to have if it was done right.
I think this is a great idea!
There are already tons of "dating sims" (what they're most commonly called in my experience) in the Japanese market (straight mostly, but some gay...most of them tend to be anime/animated though [which I'd love to see content for too], but there are some more realistic ones).
As someone mentioned, thrixxx also does sims like this (though less story based than "action" based - the Japanese sims still have a lot of action but often have more stories where you make choices).
Would love to see RealTouch eventually adapted to this stuff...