What would you recommend/what do people do for power and access for in-wall sensors? Pulling power at least once per room (assuming you can share at least 1 node with another room) and being able to access it if you need to reflash feel like hard problems.

OR, am I completely missing the point that it's "through walls", not necessarily in-wall (though that would work). A wall-wart-sized device containing the ESP32 board could be plugging in to each room and share the node (on the opposite wall) of the next room?

Very cool project and love the HA integration as well. I'm using PiR and mmWave (Z-Wave and Zigbee) currently but obviously you either have to run power for those or deal with replacing batteries, this seems much more maintainable and unobtrusive.