

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.
1970 was during the cultural revolution. In that year, the world population was 3.68 billion, and the population if China was just shy of 830 million - China had 22% of the world’s population, so if they held (only) 20% of the world’s prisoners, they’d have a lower than average incarceration rate.
The same is not true for the US today, we have less than 5% of the world’s population today.