Well as some one who actually played the game. The game was more akin to a work out video. There was no input device. You just watched and carried out the exercises. And you entered your data with standard controller.
Now I haven't played wii fit... But it supposedly tracks your movement accurately and such. So in fact, there is input to the game and some games are dependent on your input to do well.
I think there are familiarities....called fitness.