I came across this article on the dual purpose bicycle and while I find it pretty nifty technology it doesn't seem like it would be much fun to ride. Perhaps even dangerous..."a circular saw".... I'm trying to figure out where your right leg is supposed to be while pedaling the above bike.
A dual purpose bicycle (DPB) is a bicycle which can be used for both transportation and for power production. The modification consists of a free wheel, a bottom bracket and a “V” pulley. The DPB can power a rice thresher, a peanut sheller, a circular saw, a wooden lathe, a piston pump and many other implements that require rotary motion.