Game Stop told us they get at least one a week, but they sell very fast. I believe it comes with everything you need to play, but there are also games you can purchase separately.
I'm anxious to get one, but I am also okay with waiting. I'm keeping my eye on Sears.com as we have almost the exact amount we need left on our Heroes at Home Sears gift card.
In case you aren't familiar with it at all here is a link to a great review of the Wii Fit. And here is Nintendo's Official site for the Wii Fit with some great info.
If you ARE familiar and you've played with one yourself, I'd love to hear from you! Tell me what you think!