I used bluez and bash to lock xscreensaver using some very minimal bash. It wasn't my idea I believe people on the Gentoo forums were doing it.

But you can just loop over something like `hcitool rssi "$MAC"` and project it somewhere, there's a variety of ways.

I like using dunstify with the -p option to persist on screen.

I think it's really impressive what these agents can do, but you should also consider whether you're asking it to burn tokens reinventing the wheel for you, or making a pretty wrapper around a wrapper.