Potato/Fruit powered digital clocks have been on the market for well over a
decade.

Edmund Scientific still sell one for $19:
http://www.scientificsonline.com/Products/DisplayProduct.cfm?productid=1026

Paul

> many many years ago, I used two potatoes to power a small watch.
> I sliced off the top of the potatoes (don't boil or fry :-))  and
> inserted a copper plate and a zinc plate (size about 2 sq cm each
>  inside the potato). As far as I can remember I got about 1.6V
> when they were connected in series. The watch kept running about
> three weeks until I accidently dropped it into the floor. But
> that time about 5 % of the zinc was gone, so there was quite much
> capacity left.
>
> This was really something which attracted people, made them
> interested, asking quiestions... Maybe it has a commercial potential ? :-)

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