About 10 years ago i had HomeAssistant running and thacking my bluetooth devices. It does so per default by jus memorizing a mac adress an recording when it's visible and when not. No need for pairing or anythung. It also stores the custom name if available.

Anyway, the default dashboard also automatically generated a view when my neighbours "Katie's iPhone' was at home and when not, until I actively deleted it and the data it stored.

Similar story - "Home assistant picked up my neighbours Bluetooth toothbrush and now I can see when they brush their teeth"

https://www.reddit.com/r/homeassistant/comments/1306pcw/home...