I use a Freestyle Libre in conjunction with a miaomiao which reads it automatically every 5 mins and sends the reading to my phone via Bluetooth.
There is of course a phone app but also a watch app and complication to display the reading. However Watch OS has a limit on the number of times a complication can be updated in a given day (reason why Apple Watch has no live pedometer complication)due to battery limitations, so I find myself having to manually check readings.