Room detection

So, I have been tinkering with hassio for a while, and starting to get a little hang of things. The next step on the ladder is to learn how to set up room detection, let my pi3b+ know that i am entering my home office. Anyone of you have a good way to do this. I was thinking this must be possible via my android phone, as I already use the households phone to track where the family is, but that is more coarse location like, home, work, training or similar.

Kind regards
DigiNorse

Bluetooth trackers or some other short range tracker

I tried FIND for a day and it worked