There's a bunch of gizmos coming on the market in the next few months. The Terrastar looks to be pretty good. It's windows based so you can run about everything on it like a number of GPS mapping programs. I've been watching their web site, though, and there's been no updates which seems strange if they're claiming a 1st quarter release.
However, SPOT and Delorme are about to come out with a texting capable locator. I've heard it'll initially have text-send capability, followed a few months later by receive. Other text locator beacons are also supposedly to appear in the next couple of months.
Which is all to say that unless you need it soon, I'd wait until June or so to see what's out there. If you rent or buy a current model Sat phone, you'd want an Iridium based one for the Sierra. Global Star doesn't seem to work well, as of last summer anyway.