WIYF (Wikipedia Is Your Friend):

http://en.wikipedia.org/wiki/Iridium_Satellite_LLC

Iridium is a company that runs communications satellites and provides satellite phone service. Since they run a constellation of LEO satellites in a non-equatorial plane, they provide seamless worldwide coverage.

The downside? Cost. Phones are expensive, calls from the handsets are expensive, and calls to the handsets are expensive--often more expensive than even non-disounted international roaming to most countries.

It's designed for people who want or need to be reachable anywhere on earth--executives flying to remote hunting/fishing lodges in Alaska where there is no cell service, people hiking remote mountains, people sailing across the ocean, etc. And it's mostly for voice: while they do provide transparent TCP/IP data connectivity, it's at speeds slower than dialup modems (and with nearly two full seconds of latency).

For voice, it appears slightly cheaper ($1.39/minute) than what the cruise line wants to make calls from their ship, but data connectivity is worthless, and once you're on land, even international roaming is the better option (with the $5/mo voice roaming package, calls to/from most major countries are about a buck a minute).

Still, it is an option...