

In a poly relationship with n members, there will be 2^n - n - 1 interpersonal relationships in play.
This is the cardinality of the power set of n, minus the number of singleton sets and the empty set.
Thought i would mention it, just in case you needed a quick way to calculate the number of relationships in ur polycule for ur therapist.
ZigBee is Bluetooth, so controls can be done entirely locally.
We have Aqara (ZigBee) water leak detectors for our sink and basement, a 3rd party USB ZigBee dongle and a raspberry pi running home assistant. This gives me a discount on our home insurance that is more than the devices. Everything runs only locally.
(Admittedly I am not including the cost of the pi, but you could salvage an old laptop or something instead. My pi has other things on it other than HA, its multipurpose)
I also have some WiFi RGB bulbs/led. Using home assistant I can swap their colors for the holidays and I never have to decorate again. I’m lazy, and I hate Christmas.