Old Android phone as Bluetooth sensor

Have been experimenting quite a bit with my Hassio / Docker setup for the past couple of weeks and got things configured fairly well. One thing that isn’t working as well as I’d like is presence detection - using GPS and the Home Assistant app, it’s not quick to respond, particularly on my wife’s Galaxy S8 (she still shows as home for around 30 minutes after she’s gone from the house). Doesn’t help matters that my router won’t support NAT loopback. Was thinking about using a Bluetooth sensor instead of a GPS sensor but was wondering if it’s possible to use another device, like an old Android phone, instead of purchasing a Pi.

Thoughts?