I am not aware of any Smart watch working directly with Libre.
You will need to install an alternative app on your phone which can post readings to a smart watch.
There are a number of options available if you are technically minded (they are unofficial and written by techies for techies). You could add a Bluetooth bridge as suggested above or hijack theBluetooth signal which comes from the sensor for alerts to another app. You need to consider whether you need your readings on LibreView for your diabetes team, whether you want the graphs to automatically back fill, how technically minded you are to set it up, update it and troubleshoot when Android updates your phone, and whether you want to spend money on the bridge which makes the sensor more bulky so more likely to be knocked.