Interesting! I have the Wii and Wii Fit in my Tech Lab...but have not the Wii Fit for curriculum purposes yet...it's there as an incentive and for "Rainy Day Wii-cess" when the kids can't go outside. I've used the Opera browser to access educational websites too...kids love to play with the wii - and doing anything can be fun on the whiteboard. I'll be looking to see what ideas others come up with.
Well, the main thing I can see the wii fit for is physical education. You could use it as a way to teach the kids the muscles and bones of the body, which muscles are the most important, etc. It can also be used as a collaborative tool to allow students to work in groups and whatnot.
It's not a Wii Fit game, but Tiger Woods Golf is great (regardless fo your personal opinions about Mr. Woods).
The game is very realistic and incorporates wind direction and speed, angles, slopes, a smoother more pendulum swing will generate more force and better contact with the ball than swinging as hard as possible, and so on. All the aspects of real golf. Using it with students, having them determine where to aim based on wind of slope can not only be fun but educational within the math/science realm.
I work at a ymca gym that has a room for elementary children to play in while their parents work out and we have a Wii for educational purposes. There is a game called Wii Spelling Coach that can help with spelling and vocabulary. There is a game called Wii Music that introduces instruments and classical music that can get children interested in performing music.Nickelodeon has a line of Wii games that are educational. Also the Wii fit games are great for keeping kids in shape and active! Hope this helps!