After having messed around with trying to detect if showers or bathrooms are used (humidity rising takes about 10 seconds so not great for knowing if a shower is in use), a possible double whammy…
As i also finally found a use for these aqara vibration sensors .
If you have the right shower or bath faucets (modern ones probably work best) just place on of these on top/to the side. Measure if the angle changes (vibration, unlike angle, has a 1min timeout) and wham, instant response if the shower or bathroom is in use. You might need 1 or 2 per bathroom, depending on what kind of valve you have.
Ofcourse waterproofing these things is the test i’m currently running, but for now i plastidipped them so we’ll see how that holds up.