At Penn State Mac Admins 2017, Mike Lynn (aka frogor and pudquick) demonstrated something he built for the Hack-a-thon -- some code that reacts to a push-button Bluetooth beacon he obtained:

https://gist.github.com/pudquick/9797a9ce8ad97de6e326afc7c9894965

The Bluetooth beacon button @frogor used appears to be one of these:
https://proxidyne.com/products/bluetooth-devices/beacons/wearable-ibeacon/
https://store.proxidyne.com/collections/maker-products/products/button-magic

PSU Mac Admin attendees got a Tile Mate in their "swag bag" -- this is a BTLE device used to help people keep track of and locate items.

https://www.thetileapp.com/en-us/products

The Tile Mate device has a button, so I wanted to see if I could modify Frogor's code to work with the Tile device.

I was mostly successful -- try it and see.

If you've already set up your Tile device, to play with this code:

1. Turn off Bluetooth on your iPhone or Android phone you installed the Tile app on. (If you don't do this, the Tile device will talk only to the phone and this code won't see the needed Bluetooth LE advertisements.)

2. cd to the directory containing the tile_lock.py script.

3. Run the script: ./tile_lock.py

4. Double-click the Tile logo on your Tile Mate. Your Mac's screen should lock.

5. Wait 10-15 seconds until the Tile Mate stops beeping, then double-click the logo again. If the screen is still locked, a fake car alarm will go off.

6. Back in the terminal window, control-C to stop the tile_lock.py script.

As written, this code will react to any Tile device in range. It could be easily modified to react to only a specific Tile, but I'll leave that as an exercise for the reader. Some hints:

1. Uncomment line 81 to get the proximity UUID from your Tile.

2. Edit line 2 to replace the UUID there with yours.

3. Uncomment line 83; comment line 84.