A think a key success factor to health IT really becoming a part of our every day lives is the ability for healthcare platforms to aggregate data from hundreds of input sources to create real intelligence around healthcare. The Kinect would surely add an interesting twist on augmenting all of that data.
I've been hacking on a project like that -- WiiScale is a Mac app that sends your weight (captured from a Wii BalanceBoard) to Google Health. Since it knows your height, it gives a realtime visualization of your BMI while you're on the scale.
Video/Download here: http://snosrap.com/wiiscale/ Source: http://code.google.com/p/wiiscale/