The Water Powered Calculator

Solar powered calculators are so old school.

Runs on water – no need for a light source! Plain tap water powers this unique, H20 desk calculator! Add a few drops of water to the removable battery and insert it in the calculator for up to three months of use. When the display begins to fade, just refill the battery! It’s more reliable than a solar-powered calculator – and friendlier to the earth, too.

You can get one for $24.99 from here. [via]