I have been riding my make-shift stationary recumbent exercise bike for about 80 minutes so far and it is giving me a great workout. However, riding a stationary bike is quite boring. It would be a great idea for someone to invent a virtual reality bike that allows me play a racing game and control the tank, bike, or car with my bike. It would be even better if you could change scenery (or levels), make your own scenery, or even race against other people.
It would be good if such an invention could allow you to simply plug your bike into a spare TV.
Update: It seems as if someone has already come up with this idea. See Virtual Bike Improves Safety. What I had in mind though is a cheap, mass-produced recumbent bike that can easily be plugged into the TV. The software will already be in the bike's computer. The virtual bike in the BBC article is for a motorbike and the equipment looks very expensive. Given that obesity is set to rise in the future at a rapid rate, such an invention I'm sure will be very popular.