Not sure exactly what use case you had in mind, but the new device class of MM wave sensors is frequently used for detecting that a person is in the bath/shower even through a glass door.
Originally most “motion sensors” used with home automation systems were actually PIR (passive infrared) sensors, detecting small changes in heat as it moved across the lens. Not only could they not detect through glass, they were particularly unhelpful in bathrooms because of the rising heat and the inability to realize that there was still someone in the bathtub or the shower.
In contrast, MM wave sensors are actually detecting motion, and they can detect even “very fine” motion like a person breathing. So for the last six months or so, we have been seeing more and more people adopting this device class for many of the bathroom and bedroom use cases.
In many situations, this eliminates the need for a humidity sensor all together, since in the past people frequently used rising humidity as a way to proxy for a person being in the shower. Now that is no longer needed: you can actually tell whether a person is there or not.
Here’s the community FAQ if you’re interested:
Best mmWave Sensor to Use with ST? (human presence sensor/occupancy sensor)
Of course, humidity sensors still have value for environmental controls, like greenhouses, musical instrument storage, comfort in dry climates, etc.
So it all comes down to the details of why you wanted that information. 
