We bought a SPOT several months ago, but haven't needed to use it yet.
We didn't pay for the "follow us as we travel" feature (as I recall, it costs around $50 per year), because we put our location on the Datastorm Users map so anyone so inclined can see where we are by going there (and it's free).
The only drawback I see in it is the "ask for help" feature where, in a non-emergency situation, you contact your "SPOTTeam" members. They get a canned email or text message, but there's no way to indication "what kind" of help you need. The only situation I could come up with where we might use the "ask for help" feature rather than the "9-1-1" feature is if we were stranded along the road out of cell phone range and needed a tow, a tire change, etc. I've instructed our "SPOTTeam" members to call the State Patrol in the state where we are (the email/text message contains a link to the map showing our location) and give them our location.
Hopefully, we'll never need to try it out.
2014 Winnebago Aspect 27K
2011 Kia Soul