I've just noticed that it is possible to run Bluetooth LE device scanning while Raspberry Pi is connected to and even playing to a Bluetooth speaker.

in pCP can run
hcitool lescan
(don't use "hcitool scan" while playing as it music breaks up)

Wondering about how to use this ... e.g. player in kitchen is started automatically with specified Favourite or Playlist (with matching between Bluetooth device and Person and Person to Favourite/Playlist)
if not already playing (perhaps also not "off") and time is between 06:30 and 22:00

I expect that this could be done fairly easily by using HASS and Room Detection but doing it without having to install full home automation could be fun ...