reelyActive Smart Spaces Revisited might be useful for you. With a fob you don’t have the problem with phones spoofing their BT addresses.
If you are running on an RPi 3, I’ve found that the on board BT interferes with the on board WiFi so you might not want to run this detection on the same RPi as OH unless that RPi is wired or you have a BT or WiFi dongle instead of the on board ones. If you are not running OH on an RPi 3 then no problem with the BT bindings.