Pedometer tamagatchi.

Had this idea for a weight-loss, weight-management thing. Pedometers are cool when you realize you walked 20 miles in a week, holy shit, but as they go, the ratio of gain seems to mean less. So this would be a tamagatchi-like creature who will get fat if you don't walk a certain amount of steps every day. Maybe you can input your daily caloric intake or whatever so you break even, but yeah, I mean, basically, that's it. You're not walking for some stupid number, you're walking to keep your creature alive.