Some very clever man has turned an exercise bike into a device that is capable of interacting with a console so that you can play Mario Kart whilst burning calories. It’s pretty awesome, and surprisingly simple. Basically, cycling forward is the same as holding down the accelerate button, and then left and right d-pad buttons are built into the handlebars.
Does this make sense?: Yes, but how many people really want to put that much effort into a video game. I get tired after 5 minutes of Wii tennis.