My feeling is that if Apple, who have been researching how to make a smart watch take blood sugar readings for over a decade and haven’t managed it yet, then these current ones available are at best wildly inaccurate and worst don’t work at all.
If you just mean getting readings on a smart watch from a CGM such as Libre then yes there are some apps that will display your current reading from the sensor to your phone, then to your watch.
Edit to clarify.