Whereas, in contrast, the Garmin inReach devices need "only" a clear sky view.
If you use it a lot, you'll start to increase your fees, I'm on the next higher plan which I think is $35/m. I should revisit that, it's a lot over a year ;-)
They have the basic devices (connect with phone, or emergency button), I have the one with maps built in. That one is awesome, it has worldwide city and trail maps. Maps works without a subscription, but I do use it for trips where there is no phone service more to get text messages.
You are supposed to register it with the local government org. In the US, that is the NOAA. When the PLB activates, the receiver which is either the Coast Guard or Air Force will attempt to contact you before they send the distress call to whatever local S&R there is. Obviously if they can't reach you, they will send help anyway.