Getting auto unlock feature in my mid-2012 MBPr
I found on the web a way to get auto unlock feature (using the apple watch to unlock my mac) working on my mid-2012 MacBook Pro Retina. All that I had to do was change my airport/bluetooth board for the newest one.
I bought Broadcom 94360CS from iFixit and changed it very easily. I had macOS 10.12.3 installed. The wifi worked just out of the box, but the bluetooth was missing, so I went for a fresh install of macOS. Wifi ac, bluetooth and auto unlock working like a charm!
Just reinstall from scratch.