The Wii Fit fitness system for the Nintendo Wii is shipping in Japan and Play-Asia offers it to the rest of the world for $189.90.

So if you want to get a head start on the Wii Fit, you can get the Japanese version now.
Nintendo announced the Wii Fit at E3 in July. Wii Fit is a sensor mat called the Wii Balance Board combined with exercise software. The Wii Fit mat measures your movements and senses if you are doing the exercises right.
The exercises are displayed by 3D figures on the screen. Indicators tell you if you are doing the exercise correctly and at the right pace.
You can choose between Yoga, muscle toning, aerobic, and balance exercises.
The earliest the Wii Fit will ship in the U.S. is January of 2008.
See also this Wii Fit video.