You can just call me mired in ambivalence on this one. Okay, you're doing the Annapurna Circuit. I get it. But people have been doing that for many years without the benefit if constantly beaming their location back home. I really don't think doing so is a BAD thing—I'm hardly a Luddite when it comes to technology—but I do question its necessity. Whatever happened to splendid isolation?
Anyway, while I think the Spot II ($150, plus $99 subscription to access SPOT satellites for sending messages) is a pretty good gadget. It's a GPS device that allows you to send simple messages to the outside world ("I'm OK!"), the device isn't yet functional in the part of Asia where you will be traveling.
I'd go with the ACR Electronics SARLink Personal Locator Beacon ($400). It works everywhere, and is designed for emergency use by search-and-rescue teams. It can bring people to within 100 meters of your location. It's also very tough, and has long battery life of up to 35 hours once activated.
Now, keep in mind, the ACR is not a communications device. You can't use it to send messages. It is an EMERGENCY device. Which I think is the right balance. You and your family will have some peace of mind knowing you have an effective electronic beacon, minus the over-sharing aspect of constantly sending "I'm OK!" signals. Maybe I'm being cranky, but there it is. And if you have to have some sort of non-emergency message, you can upgrade to the 4.6link.com non-emergency message surface, though coverage in Asia isn't guaranteed.
Anyway, you'll probably bump into people with satellite phones. So take some little bottles of Scotch whiskey or something to trade for a phone call out.