

WaterSeer was initially somehow related to some part of UC Berkeley, rather than MIT.
You may be thinking of this device: https://www.cell.com/joule/fulltext/S2542-4351(20)30444-X
… Or the metal oxide framework predecessor to it, or the newer thing that uses some sort of gel.
I’m not aware of a commercial product based on this work.
If small numbers are much more frequent, it’s better to return early. Really, you should gather statistics about the numbers the function is called with, and put the most frequent ones at the top.