We used a SPOT on a 15 day charity cycle tour from Toronto (Whitby) to New York City (Coney Island) a couple years ago, and I would not be excited to promote the system to anyone.
1. Battery life is about 2-3 days with the unit running from 07h00 - about 18h00 each day. If you need it running 24hrs, you will go through a lot of batteries.
2. Signal delay is bad. A cop came out to escort us into Albany NY as a publicity thing. He never found us until we were at our rest house for the night. When he did catch up to us, the signal still showed us on the trail way out of town still. Not really confidence-inspiring.
3. Related to above, message delay is bad. I would ping "mission control" (my wife) each morning to let her know we were hitting the trail and to activate our website/mapping/social media, but often she would not receive the message until after lunch. After three days of this, we switched to just texting her. If this were a low level call for help, we would be stranded for hours before receiving aid. If it were an SOS, we'd be dead. The sending unit was mounted on top of my panniers facing the sky, unobstructed, so it wasn't because it couldn't see the sky.
4. Subscription is too damn high for the service quality. IIRC, the unit cost us $200 and the subscription was another $200. $400 for a device that was used twice and barely functioned is too much. We cancelled the subscription immediately after our ride, and the unit is sitting on a shelf.
5. Trip sharing is shitty. If your purpose is to provide a "follow me" type experience with live updates to a website and followership, the SPOT has (had) no way to do that through them as an embedded window. We had to daisy-chain the GPS waypoints to a third-party mapping site, which would then display placemarkers, and in turn send the mapping to our live website in an embedded window. Even googlemaps has an "embed" code. We ended up tracking through
this site. - Also, SPOT dumps your data after a year, so you better find someplace that will host/store it if you want to save it.
6. Canned messages to social media were junk. It was just a text line that flooded our feed and turned off followers/sponsors. We lost gobs of followers along our ride and afterwards the feedback was that the 30 or so messages a day, all alike with no information was a pain in their feed. I can't tell you how much this cost our campaign, but we won't make the mistake again.
Basically, whatever you get, do some field testing first. This was a product I was excited about and really believed in both as a safety and promotional piece, and it thoroughly let me down on both fronts.