I've got some of those Xiaomi sensors. I've not hooked them up to HA or the likes yet but I used a Python script found on github to check temps. They're encrypted so they had to do a bit of reverse engineering if I remember correctly. They can be flashed with another firmware which should improve battery life as the client won't have to connect to the device each time to get values (I think the third party firmware changes them to broadcast values).
Got my Conbee II today. Quick delivery from Amazon Germany.
Got my Conbee II today. Quick delivery from Amazon Germany.
Hmm. One of mine is about 4-5m above the receiver through a thin ceiling and sometimes it struggles. You could use ESP32s to read them though I think.They will all be within about 10 meters of the bluetooth receiver, hopefully that's close enough for reliable communication!