Self-implemented Workout Requirement
A feature that FOR A SHORT TIME locks you out of accessing your games/apps until you've completed a daily amount of exercise.
This SHORT-TERM added motivation would hopefully be enough for some people to make that workout a part of their daily routine.
Create your own generic app, like the Nintendo Wii's Wii Fit for example, or allow the use of other fitness apps.
Maybe just make this setting prevent access to WiFi until enough kj have been burnt by the user, but make it completely OPTIONAL.
[Caps Lock was used to highlight certain points for those that don't read everything before disagreeing]
Ace Of Spades commented
Dude that's why there are games like superhot
In general, I think it would be a nice idea to add a fitness mode to the Quest. It would add another market for the device.
While the idea of forcing the expenditure of calories before playing non-exercise games is a fine option, I think that there could be quite a few other aspects:
Add calorie tracking. Put that value in a highly visible place in the interface.
Distinguish between exercise apps and other apps. This could possibly be automatic, by tracking the amount of exercise that users get from an app. This could also give a score to the apps of how effective they are for exercise.
Put the exercise apps at the top of the home/library. Overlay them with figures such as use time - average, last day, today - and estimated energy burn.
Add global achievements for exercise, beyond what the apps might provide.