The ones used in gaming machines in australia for the last 4 years use lasers to weigh the coin and various things.
Yes, there is nothing to stop you selling it. Many ideas have been killed through greed though. Classic example is of a ceramic alloy that was patented, wears less, cheaper to make and better fuel economy when used for engine parts. Who bought the patent for it from the inventor's ? BHP billton. Wonder why ?.... The alloy has been used in one car engine to date from memory and that was a mercedes and it cost them a fortune.