macOS Sierra debuted a new feature called Auto Unlock that lets you get into your Mac without typing your account password simply by wearing a passcode-protected Apple Watch. With Auto Unlock, you just wake up your Mac and if it senses you're nearby and wearing your watch, it'll log you in automatically. Yes, it just works!
Auto Unlock imposes certain hardware pre-requisites in terms of modern Bluetooth and Wi-Fi chipsets. Here's how you can quickly check if your Mac supports Auto Unlock.