“Motorola’s messaging service works just like SMS, but it can only be delivered to other people running the special Bullitt Satellite Messenger app. The service will do SMS forwarding, though, so if you punch in a random number, that person will receive a message prompting them to download the Bullitt app so they can talk to you. It’s probably best to set this up with someone beforehand, but it sounds like a great way to communicate when you’re off the grid.”
Probably similar in terms of service offering. They could differ in terms of cost and coverage. The Bullitt service now currently covers U.S. and Europe, but it targets to have wider global reach by Q3 to Q4 this year, from what I’ve read - https://bullitt.com/ .
Personally, I use a Thuraya satphone apart from my ham radio gear as alternate/contingency comms. Satphone tends to be expensive per message or call, though. Advantages of the satellite messaging services over satphone is that compatibility with terrestrial networks (cellular, wifi) when available. I wonder what you guys’ thoughts are.