I personally chose not to automate turning on our shower lights, though I do automate turning them off after no motion.
When a shower light turns on the ceiling exhaust fan turns on and it will remain on until 15 minutes after the shower light turns off. Also my hot water recirculating pump starts when any of the shower lights turn on. We have gotten used to turning on the shower light a few minutes before a shower to let the pump bring hot water to the bathroom.
We automated the shower lights and bath fan based on the shower itself (Moen u) and espresense. If the shower is turned on through Alexa, HE or Siri (or locally), the shower lights and bath fan come on. A double tap of the shower light switch also turns on the shower, the bath fan and the lights. 15 minutes after the shower turns off, the bath fan turns off and the shower light returns to its previous state. Obviously, it’s a little late for you to add in wall plumbing components, but…
We have Esp32’s mounted under our WC and bathroom counters. I charge my watch on one of those counters and we each set our phones on the other one when showering. Espresense dictates shower temp and brightness. I prefer a warmer dimmer shower. My wife prefers a cooler brighter shower. From there, we automate unique post shower automations as well.
As an aside, when the shower turns on, if the bathroom tv is on, the TV’s internal speakers automagically switch off to allow for only the Bluetooth speaker in the shower to play audio. When the shower turns off, the TV’s internal speakers come back on.
Thanks for the link on that battery operated mmWave sensor. I think I'd still need it for the tub, but I'm trying that mmWave in the toilet now to see if it works through tile or at the very least notice the water flowing in pipes? It can actually be an ideal spot as we have an outlet in there. Ugh I could have sworn we had more outlets in this room other than one at the vanity, but I guess we don't 
I'll let you know how it goes!
I use an Aqara motion sensor. Just the basic v1 sensor with their stand to angle it down toward the occupant. It's in a corner near the door, situated to that only the person in the shower can see it.
Steam has had no effect on its life or performance in the 2 years it's been in use. I use HA with Home Assistant Device Bridge and its performance is consistently good. If you pair one of these directly to HE, then YMMV.
This turns on both the shower light, and the bathroom fan. This works so well because the sensor is tucked in a corner, so anyone using the bathroom for anything other than a shower does not trigger the shower lights or the fan. The sensor keeps the shower lights and fan active as long as there is motion. Once no motion is detected, the shower lights time out after 5 minutes, and the bathroom fan times out after 20 minutes. This works so much better than trying to trigger the fan via humidity.
The sensor is affixed to the tiled shower ceiling via the standard (and very sticky) Xiaomi double-sided adheisive that comes with the sensors. No sign of it loosening in even the slightest from the steam (and I have a teenager, so you know it gets mighty humid in there, for a very long period of time). I cleaned the tile with IPA first to ensure it wouldn't come loose.
Just FYI. The answer is "Yes. mmWave presence sensors work through tile." Responding to you in the shower right now. Just chilling here for about 5 minutes to make sure the presence sensor remains "motion active" sitting on our teak bench lol. Plus a presence sensor in there will be better than a motion sensor just in case someone wasn't having a good day or just chilling on the throne haha
We learned the second time around on bath remodels...more outlets = more happiness. Favorite is one in each bath is the one we put on the side of the vanity near the wall. So nice to have a "hidden" outlet that we can use for stuff on the counter when we don't want to see the cords or install an outlet on the wall. Example below:
Beauty from above - meets WAF standards - no visible outlet stuffed into the mirror/wall for the toothbrush, no cords on countertop: 
The hidden mess:
BTW - I don't know how you guys survive w/just one outlet over the sinks!
Great news, you get a two-fer, assuming the mmWave positioned to sense motion in the toilet area as well as the shower!
It's one of the few places where you can close the door and be assured of some quiet time that no one will interrupt until you come out. (Except the cats and dogs.) 
I totally forgot that we had an outlet placed in our bathroom closet (across from the toilet room) because we had lofty dreams of putting a minifridge for beer whenever we get around to getting a jacuzzi for our jacuzzi deck (which is just off this bathroom). If this 24G presence sensor at max sensitivy & distance can detect presence in this whole bathroom, I will be thoroughly impressed.
Aint that the truth! One on each side of the mirror (with usb outlets) couple of other strategically placed ones. Also one behind the tub and one behind the toilet plus the one in back of the mirror (because it's a heated mirror) Same with every room in the house. Each bedroom has a minimum of 8 outlets.
For anyone curious, I went with the 5G mmWave presence sensor in our toilet room, where there is an outlet above the sink in there. I have it pointed towards the shower wall. It is able to penetrate through dry wall, tile, and plumbing. The shower light is turned on by a door contact sensor and is then turned off when the presence sensor motion is inactive. This way the motion sensor does not trigger turning on the shower light when you're just going to take a piss. Yes, I'm one of those weirdos that likes to use Basic Rules lol.
That's likely an illegal outlet. At least in just about every place in North America I can think of it is. Cannot below sink level. Hopefully you have that connected to another GFCI outlet? I'm not policing you, but do not want you or anyone in your family to be electrocuted. 
Yup, it's on a GFCI circuit. Thanks for asking.
Officially inspected and passed, so either it's allowed, or the inspector missed something. 
It's allowed here as long as it's on a GCFI protected circuit. It also must me 20amp...(Kitchen and bathrooms by code must be 20 amp)
During an addition in 2017 electrician added an outlet under sink inside the back wall of the drawer box so my wife’s hair drier could be plugged in all the time and stay hidden within the drawer. Like @danabw and @rlithgow1 said it’s on a 20A breaker that runs on the load side of a GFIC outlet by my sink.
I see this no different than outlets in kitchens under sink for disposal which code allows.
The only issue I see with that plug placement is water on the counter could roll into it... I mean if something happened obviously it would trip the GCFI... That's just my thought though.
How are things working?
Happy husband? Be nice if we had a husband version of "Happy wife, happy life." Happy hubby, drinking bubbly? 
Outlets? In the bathroom? That's crazy talk! 
The bathroom next to the bedrooms has a single gang box. It originally had a light switch and a single outlet. I've changed it to a duplex outlet with a double gang faceplate and a Pico remote. So now I have two whole outlets.
Still no counter space however, the sink is just attached to the wall. The sink and tile is a lovely midcentury Venetian Pink. The original house was built in 1954.
Haha I love it! He is happy with the new automations for sure! Thank you again for the help. The human presence in the water closet was definitely key
There’s another option to power the mmWave sensor which is via Power over Ethernet. Cat5 or cat6 cable can be run at pretty decent lengths from a main POE switch elsewhere in the house, to even places you don’t have an outlet available. I’ve done this in several places in my home, a basement shower area being one of them. I have a POe drop in my basement drop ceiling that I have this device (Amazon.com: IPCamPower POE Powered 3 Port Switch & Network Cat5 Cat6 Midspan Cable Range Extender Pass Through Repeater for IP Cameras - Run Cables up to 1148' : Electronics ) plugged into, and from there I ran a few cat5 cables to different devices (motion sensor and another for mmWave). I found the mmWave sensor works best in the shower ceiling but not inside the shower. I have a zigbee contact sensor on the door so when the door opens, light comes on. Light goes off after 15 minutes of no motion in the shower from
The mmWave sensor. I use motion sensors to turn the overhead lights on in the overall bathroom. Works for us.
Download the Hubitat app
