I was looking to automate a shower Extractor Fan as I don’t find the ones with the inbuilt humidity sensor very good.
So: Aqara Humidity sensor placed somewhere in the shower. Near the fan. Occupance sensor. Sonoff switch to trigger the fan.
If the humidity is > than threshold and the occupance sensor is active = turn on fan.
I was looking for a good ZigBee occupancy sensor though , the aqara fp sensor look all wired and not battery operated.
Rather than activate the fan over an absolute humidity threshold with occupancy, I’d recommend setting the fan to turn on when the room’s humidity is a certain amount more than the ‘normal’ humidity and ignore presence.