Actually GlobalStar has some of the weakest satellite coverage in the satellite market. It covers North America and Austrailia very thoroughly. But only covers other continents partially. It covers 3/4 of South America, only western Europe, and only really covers Japan and Singapore in Asia. There is almost no ocean coverage.

The Iridium network (which is what Garmin uses) covers nearly everything outside of the north and south poles. This includes all the oceans and basically all habitable land. That is why Iridium has dominated the satellite market for so many years over GlobalStar. Garmin satellite devices (like InReach) uses Iridium. But they also have non-trivial costs associated with that coverage.

As someone who has used these satellite communicators for years, don't get your hopes up on using these all the time like an extension of your phone. Sending messages over satellite is painfully slow, even with devices with advanced helix antennas (which the iPhone doesn't have). It can take minutes to send a single text message. Phone communicators sometimes have 20-30+ second lag in them.