lol...they beat me to it before i was born!! so much for that patent!!! i do think it would be a nice little novelty and a bit of piece of mind for the old motors.WICO thought the same thing as you. This has been listed for a while now, if it was a bit cheaper Id buy it for the novelty.
Vintage Antique Marine Outboard Engine Boat Temp Alarm Wico 1950 | eBay