
If I'm understanding your mock-up, you're looking for real-time finger detection in the live video feed? It would be really cool to be able to place markers on the fingers like that so you could see exactly where they needed to go.
Incredibly hard problem. Something I've been thinking about for years though. (There are some ancient forum posts to that effect someplace.)
Not only is video lag your enemy there, but your detection and tracking has to also be done almost instantaneously too. Add to that how many wacky shapes you can get your hand into where one finger is covered by another, or how at that particular camera angle you can't quite see things perfectly, or there isn't enough light in the room to get a good clean signal...
Still, it's sort of the holy grail, isn't it?

I would love to do that.