This clock runs on salt water. The briny fuel corrodes the clock’s electrodes, which release electrons to provide power to the monochrome LCD. Though it doesn’t do much more than tell time, it can go weeks without a refill.
Other water-powered clocks tend to look like they were made as a science project, but this one is available in a handful of different colors and screams eco-chic, not eco-geek. It is available for $16.