NunuXD
Make Wii Sports!!! Have it to wear the player has to stand up while playing so the body gets a workout. Not everyone can go to a tennis court or golf course or a personal trainer. Make it go from light walk in the park to fireman or police level fitness all the way to boot camp or SHIELD level training. Imagine a 'GAME' that can make an average Joe go up to Hawkeye or Black Widow levels of fitness. You could sell it for $100 each and still sell a couple of million copies. Who wouldn't play that? If you later add Mountain climbing, Rafting, Gliding ... By the time Aliens invade Earth everyone will be at least Lora Croft levels of fitness.