I currently use xDrip, Tandem X2, Dexcom G6, and Ionic Fitbit watch. There is no direct connection from ionic to X2, but on my android phone I can see the xDrip screen or Tandem:Connect mobile app screen.
XDrip sends data to ionic, using a watchface from Glance.
I have recently heard of another lower cost watch, which also says will work with xDrip.
But have not used it.
More details
https:///jam github.com orham/xDrip-plus/blob/master/Documentation/WatchGuide.md
And another option.
Or this