What do you want to use it for?
I used Libre 2 with xDrip+ (on an Android) with the OOP2 app to hijack the bluetooth signal so didn't need any add-ons. My current blood sugar reading was always on my phone home screen and xDrip_ allowed me to calibrate, provided alarms, etc.
The only reason I stopped using this approach was to use the CGM which connects to my pump.
Some people may feel uncomfortable using unofficial apps and they don't update reports for our DSN.
I have no experience of using an iPhone or a Smart watch.