[cowpewter]

We actually kinda already have the first, in the form of the Dance Central games for the Kinect. You dance, the software detects which of your limbs aren't moving the right way, and it display visual feedback (highlighting the limb in red, reducing your score, etc) to show you what you're doing wrong, so you can perform the dance more correctly next time.

It's not good enough to produce professional dancers, but it has definitely improved my dancing as someone who just dances for fun.