If you already have a balance board and a Wii U, Nintendo would like to give you a free month of Wii Fit U. The trial program starting Nov. 1 will introduce users to the new and improved fitness game via an eShop download.
If you decide to stick with it, you can unlock the full version forever by purchasing a Fit Meter and pairing it with your Wii U via its IR sensor. The meters will go on sale on Nov. 1 for $20, making for a very reasonably priced way to upgrade for previous Wii Fit players.
Nintendo offered more details on the Fit Meter in a Nintendo Direct today (it's worth watching the beginning for the Direct Hand Motion workout, at the very least): the waist-worn device isn't simply a pedometer, but rather a three-dimensional accelerometer and pressure sensor. This allows it to not only measure steps taken outside of the game but also intensity of movement, and to detect climbing stairs or steep slopes.
Wii Fit U will launch as a packaged game on Dec. 13, 2013 and as a full game download on Feb. 1, 2014. You'll need to provide your own Balance Board and Fit Meter if you opt for the latter.