Are you sure you need voice?
I've found my Delorme Inreach (now owned by Garmin) connected by bluetooth to my
iphone to be a great solution to
offshore communication. A fraction of the cost of what you're looking at. Always works. Works everywhere. No external
antenna. It sits on my chart table and transmits through the
fiberglass overhead just fine. SMS or
email send/receive. As anyone under age 30 will tell you, if you can't say it 160 characters, it's not worth saying
They also now have a much improved
weather service - on demand 5 day
forecast for any lat/lon for $1. Not as good as a wide area GRIB but good enough for me.