WatchLock

This app will allow you to lock your phone even while it's in use.

Please note: WatchLock will disable Smart Lock until you unlock your phone using your PIN, pattern, or passcode. This will only happen when you lock your phone using your WatchLock app on your watch.

WatchLock uses Device Administrator permissions:
This setting can be easily enabled/disabled via the app

Note:
In order to uninstall this app you’ll need to disable administrator permissions. This can be achieved via the app easily or via it’s app settings.