I have tried a bunch of apps in the past which have an iOS app and a Mac app and tried to unlock your Mac automatically when your iPhone came close and lock your Mac automatically when you leave.
None of them worked well for me… until now! (cue dramatic fanfare)
BLEUnlock: Lock/unlock your Mac with your iPhone, Apple Watch, or any other Bluetooth LE devices is a free app that does this without an iOS app. It works. It doesn’t lock when I’m still sitting at my desk. It doesn’t wait until I’m a mile away before it locks.
In fact, the unlock has worked so smoothly that I thought it wasn’t locking until I left my phone in the other room.
I’m not sure why people who have an Apple Watch would use this, but as someone who can’t wear an Apple Watch, this is almost as good for auto-unlocking.
Standard disclaimers apply: if you work with national secrets, etc. you should always manually lock before your seat leaves your seat and not use anything like this. But for most of us, especially working at home, it’s pretty slick.