Running in place
What about running in place, at your home, wearing the Quest?
The Oculus Quest could simulate running recording the frequency of the movements of your arms and change the speed of the running.
This would be an eccellente fitness app.
You could use this app running in place in your room or use it with a tapis roulant.
You could run speaking with other people running through multiplayer.
You could offer different tracks like cities, mountain, lake, beaches.
You could give the player the possibility to decide where to go in some point of the day.
You could insert in the way some obstacle so that you have jump, move on the left/right or squat, to make the fitness more intetesting.
You could measure calories and create some training programs.
It could be a great fitness app, with a minimal effort.