You’re probably familiar with “[Smart Lock](https://get.google.com/smartlock/index.html)”, a feature that keeps your phone unlocked while it’s connected to a “trusted device” like your smartwatch via Bluetooth. The problem with “Smart Lock” is that it’s really not smart *or* secure — just because your phone is connected to your watch via Bluetooth doesn’t mean your watch is actively on your person or even within a couple of feet.
As such, Google appears to be rebranding “Smart Lock” to “Extend Unlock”, as [I recently discovered](https://twitter.com/MishaalRahman/status/1614774381871353858) in version 23.02 of the Google Play Services app (see the strings below). This new naming makes sense as the feature merely *keeps* your phone unlocked when it’s *already* unlocked. It doesn’t actually *unlock* your phone when it’s locked.
<string name=”extend_unlock_removal_failure_dialog_message”>Something went wrong. Try again.</string>
<string name=”extend_unlock_removal_failure_dialog_title”>”Can’t remove watch from Extend Unlock”</string>
<string name=”extend_unlock_removal_prompt_dialog_message”>”You’ll be able to unlock this phone with %1$s.
Your watch will no longer keep this phone unlocked with Extend Unlock (previously Smart Lock).
You can add your watch back to Extend Unlock at any time in Settings.”</string>
In comparison, the new “Watch Unlock” feature being developed for the Pixel Watch *will* actually unlock your device. I’ve been [tracking this feature for a while now](https://blog.esper.io/pixel-7-features-android-13/#every-pixel-7-feature-backed-by-android-13-apis:~:text=Google%20Play%20Services-,Watch%20Unlock,-One%20of%20the), and it seems to use a new API in Android 13 called [Active Unlock](https://cs.android.com/android/_/android/platform/frameworks/base/+/fe7e9e9a6dfa976abf66614a32321e93d0a3fa49). The way this works is that there are new “active unlock triggers” such as WAKE, UNLOCK_INTENT, BIOMETRIC_FAIL, and ASSISTANT. For the BIOMETRIC_FAIL active unlock trigger, for example, Watch Unlock will trigger AFTER your phone fails to recognize your face/fingerprint. Your phone will be unlocked automatically if your watch is unlocked and nearby/on your wrist (within ~1m based on Bluetooth RSSI values).
The text of the [“Watch Unlock” setup page](https://i0.wp.com/blog.esper.io/wp-content/uploads/2022/10/Watch-Unlock_2.png?w=598&ssl=1) also suggests that the ASSISTANT and UNLOCK_INTENT triggers might be used to let you perform certain voice commands and open certain notifications that otherwise would’ve required you to unlock your phone:
> Use your watch to securely unlock your phone after you wake it. This can be helpful to access notifications and your digital assistant, or when your face or fingerprint isn’t recognized.
Google appeared to show off Watch Unlock at its CES 2023 booth and [confirmed to *Android Police*](https://www.androidpolice.com/google-pixel-watch-keep-smartphone-unlocked-ces-2023/) that the feature indeed requires you to be wearing your watch in order for it to function. No release date has been given yet, but it’s something we could see dropping in the near future. Watch Unlock is a part of the Google Play Services app and since it uses the Active Unlock API as I mentioned before, it will require Android 13+ to function.
Coincidentally, [Android is adding a framework API](https://twitter.com/MishaalRahman/status/1615461533886160897) for measuring the distance between devices using Bluetooth RSSI. This is obviously not a super precise way to do distance measurements, but it should be good enough for something like this “Watch Unlock” feature. Now, due to the way the Bluetooth Mainline module works in Android 13 (it’s a non-updatable Mainline module and thus requires an OTA update to update) and the fact that there’s an API freeze, it’s possible “Watch Unlock” may not be using this exact API (it may use some internal Play Services API) or if it is, that the feature won’t be available for Pixels until a later release. We’ll have to wait to find out.