In a few countries, Samsung has started rolling out the Wear OS 4-based One UI 5 Watch update to the Galaxy Watch 4 and the Galaxy Watch 5. The update brings improved activity and health tracking, new watch faces, new Tiles, and many other new features. It also brings support for the upcoming Watch Unlock feature.
Watch Unlock is one more secure way to unlock your smartphone
With Wear OS 4, Google added the ability to unlock an Android smartphone that is paired with a smartwatch. This is similar to how an Apple Watch could unlock a paired iPhone. Effectively, you don't need to enter a PIN/password or biometric information to unlock the phone while wearing a Wear OS 4 smartwatch. This is a handy feature as you can unlock your phone when your fingers are wet or dirty, or you're wearing a helmet and can't use Face Unlock. This feature isn't available yet, and could be released with a future software update.
Android enthusiast Mishaal Rahman discovered this feature a few days ago for the Pixel Watch. However, it looks like it will be available to all Wear OS 4-based smartwatches, including the Galaxy Watch 4, Galaxy Watch 5, and Galaxy Watch 6. Later, Ærmando discovered the Watch Unlock feature (com.google.android.clockwork.active_unlock) in the One UI 5 Watch update.
Watch Unlock is not the same as Trusted Devices, a feature available on Android devices for years. Watch Unlock is a more secure method, and it can actually unlock a paired phone, provided that the smartwatch itself is unlocked using a PIN or other authentication method. To use this feature, you must set a PIN or password for your Wear OS smartwatch.