These have gotten pretty popular in the fishing fleet, since they are cheaper than the Garmin/Delorme inreach, both to purchase, and the monthly fee is usually at least $15 per month lower. Everyone I know that has used both, report the Zoleo works consistently better, both acquiring a signal more reliably, and also not having the problem of messages getting temporarily "stuck" in cyberspace.
https://www.zoleo.com/en-us