Thanks apu, that's what I was looking for. Does anyone have practical experience with Blue Link?
To me, the main use of it is really to turn on the climate remotely. For example, if the car is plugged in at home, and I was planning on leaving at 8AM, I could configure the thing to turn on the heat or AC at 7:45, while still plugged in. You can of course also do that from the touchscreen in the car. I think you can also turn on the climate when not plugged in, but that would run down the battery, and in reality nobody ever does this.
And it is sorta/kinda useful if you want to monitor charging progress. But most of the time, you have an app of a different sort from the EVSE or DCFC network, so it isn't like BlueLink is vital for this either.
If you were absent-minded, you could use it to find your car in an airport parking lot. That's another theoretical use-case that most people don't ever need.
The main knock against it is that it can be pretty slow, and sometimes times out when trying to connect to the car. My own theory is that ICE drivers rarely use the thing. If a car ever threw a CEL, I suppose it would show up in the app. You get 3 years free when you buy the car - after that I imagine that most people won't pay to renew.