Powering some led lights on bottled water. http://www.youtube.com/watch?v=-G7IO3vVcM0&feature=youtu.be (http://www.youtube.com/watch?v=-G7IO3vVcM0&feature=youtu.be)
Nice water battery!
You might be interested in these water clocks..
http://www.teachersource.com/Chemistry/GeneralChemistry/ExecutiveWaterClock.aspx
http://www.teachersource.com/BalancesMeasurement/ClocksAndTimers/ChemicalClock.aspx
yep nice, cheaper to make urself.