You can use your Watch in the Home app to:
- Activate your Smart Door Lock to lock and unlock your door.
- Receive a notification from the Home app when your door is locked or unlocked.
For the Home app to work properly, the product must be correctly set up with HomeKit.
Read the article How do I set up my Smart Door Lock in HomeKit?
However, versions 5.0.0 and higher of the Home + Security app for iOS do not support the Apple Watch app for the Home + Security app. Therefore, you cannot use your Smart Door Lock with your Apple Watch through the Home + Security app.