Wii U owners will be able to download the full version of Wii Fit U from November 1st, with the game available for free for 31 days (beginning from when the game's first played), as Nintendo try and push the system to a wider audience over the holiday season.
Note you'll need to pick up a Balance Board as well if you want to try the title out. If you purchase a Fit Meter accessory from retail (due out on November 1st) and sync it with the game, the time limit will be lifted.