Chris Welch, writing for The Verge about the latest iOS 14.5 beta:
As first reported by Pocket-lint, the new iOS 14.5 update, which went into beta today, uses the Apple Watch on your wrist to quickly authenticate and unlock your iPhone. Apple already offers this convenient trick on the Mac, but now it’s coming to the iPhone as well.
It works similarly here. You lift your iPhone to turn on the screen, and you’ll feel a little nudge of haptic feedback on your Apple Watch to indicate that your iPhone has been unlocked. The devices must be in close proximity for this to work in the first place, which is a measure to keep your data secure. (If the Apple Watch is locked, this won’t work either.) And this Apple Watch shortcut is only good for unlocking your iPhone; App Store and iTunes purchases will still require other authentication if your face is covered.
This is a very interesting feature, and one I think will push a lot of people back on the beta builds again.
It's something that probably should have been done sooner. Especially since the Mac has been able to be unlocked from an Apple Watch for a long time. Nevertheless, it's certainly going to be welcomed by a lot of people.
My only hope is that it's more reliable than its Mac counterpart.