BlueEngineer : Many thanks for all the information you have provided! I looked at the link and more information on the Garmin Inreach Mini, and their GEOS service. This may do the trick for our application, but I still want to explore the phone solution. Did you purchase your satellite equpment from one specific vendor that you can recommend?

It sounds like the Iridium system offers the best options for those who are travelling near the poles, or stuck in a deep crevace without a good line of site.

How does one know where to point the antenna with the Immarsat system?

Thanks again!