water powered gadgets

do exist after all - see here [scroll down past the wind-up radios and torches]

i'd love to know how this works

from tango group who market the freeplay wind-up radios and torches

mind you, i'm not sure how much of an advance water-powered calculators are - there have been solar-powered ones for years. and my 1980 casio scientific is still going on the original battery - and it's not for lack of use, it's been my only calculator through 26 years as a student and architect.