I'll add two and a half cents here and this is based on real world experience, including the two of us being the ones who responded to calls to go out find and rescue people - in the winter mountains on skis for over 25 years. Think about the worse winter mountain conditions you can imagine - been there, done that. Happy we could help, don't miss it one bit. Never thought of it as a fun activity, responding to someone's tragedy.
We have the InReach version of satellite communicator, but from what I understand, the new SPOT X has similar capabilities now.
We have two friends signed up as our emergency contacts. From experience, when the SOS message is sent, the dispatch center calls either of them to confirm it is an emergency. If dispatch cannot reach either of them immediately, the emergency is still immediately handed over to the local authorities. In California, the County Sheriff is responsible for search & rescue except in the National Parks.
Our two contacts have the same experience as us. They know how the system works - and how to help it along. Their job is to be our advocates, provide solid information about us and our activities and abilities, and make sure we get help. I am the emergency contact for both of them. As soon as I hear their SOS has been pushed, I'm going into action. These are people who would go anywhere to help us. We, without hesitation would do the same for them.
For responses to non emergency incidents, we'll work that out through the device's text messaging. And, we've discussed many possible scenarios.
I hope this information helps.