Being able to unlock a Mac using an Apple Watch is yet another benefit of the Apple ecosystem. For a while now, we Apple users have been able to unlock our iPhones automatically while our Apple Watch is on our wrist. But that same functionality also exists for macOS. As someone who has owned an Apple Watch for about 2 years now, I'm a little embarrassed to say I didn't even realize I could do this!
Setting up your Apple Watch requires an iPhone, and as part of the process you'll be given the option to unlock your phone using your watch. However, the feature doesn't work automatically with your Mac, even if your Apple Watch already unlocks your iPhone — you need to set up Mac unlocking separately. For that reason, it's easy to miss this functionality if you didn't know it was there, especially if you didn't know where in macOS settings to look.
