You're spot on. LIDAR sounds interesting but I don't know of any off the shelf solutions. I'm leaning towards using motion sensors like gates. Instead of point

You're spot on. LIDAR sounds interesting but I don't know of any off the shelf solutions. I'm leaning towards using motion sensors like gates. Instead of pointing them out into the room you mount them looking across thresholds like door frames. If you have enough sensors you can get a sense of direction and keep track of where people are. It is a bit fragile though. For example if two people enter a space within seconds of each other this might not be recognised effectively. It depends how quickly your motion sensors reset. I tried to use Bluetooth presence detection but it seems my smart watch doesn't broadcast its identity once it is paired with a device. I could leave it unpaired but then I lose syncing and notifications. I have seen some folks on YouTube place cameras in each room and they stream the video locally and perform face detection with it. I haven't felt comfortable enough to put cameras in every room yet, but I may bite the bullet at some point.