The Electric Power Meter
All sorts of issues arise when you're doing something that has never been done before -- like running electrical services to businesses and residences. You need a way to measure how much customers consume so you'll know what to bill them.
Edison solved this problem by patenting the Webermeter in 1881. The Webermeter contained two or four electrolytic cells with zinc at both electrodes and a zinc sulfate solution. The zinc transferred from one electrode to the other at a set rate as electricity was used. The meter reader removed the electrolytic cells at each reading for weighing, replacing them with new ones.