This sounds like its one step closer to machines taking over the world matrix style, but an interesting "what if" question.  Could batteries run off the energy our bodies create?  Our Bodies produce an excess amount of sugar energy and we have to combat that by making insulin to control it.  What if there was batteries that ran off this extra energy that our bodies create?  Its an interesting concept and one that scientists are currently working on.

The first batteries to run off this bio tech are produced using yeast.  The problem with this method is what to do with the waste that is created through yeast cells?  It can't be allowed to enter the blood stream because its toxic, this will be something that will have to be dealt with in time.  The current prototype is 15 millimetres square and 1.4 mm thick producing around 40 nanowatts of power.  A typical watch battery makes about a microwatt of power.  If this was attached to a compacitor it could be enough to power some small devices.  Increasing the surface area of the cell and altering the geneics of the yeast could increase power output.

This is pretty interesting stuff, could energy be produces using these enzymes and living organisms?  Could this be altered so that i can now eat candy bars knowing that the excess sugar is powering my ipod in my pocket?  New Scientist via Gizmodo