I read this article at
engadget.com where there is a company that allows you to turn your bicycle into a moped. Isn't a bicycle supposed to be use to burn off fat instead of letting you gain it. The wheel actually holds 23 cc engine that can get you 20mph and your water bottle holds the fuel.
RevoPower is the company that came up with this product, claims that there idea is for thise that use the bicycle to commute.
A movie about how it works can be found
here.