When people call Apple's iPhone a "global device" it's really something of a misnomer. Can it work on a desolate, high peak? Or in the middle of the ocean? No, it's limited to a network of ground-based antenna. This simple case frees the iPhone from those shackles, and lets it work pretty much anywhere in the whole wide world.
The SatSleeve from Thuraya is about what it sounds like. It's a sleeve for your iPhone, that turns it into a satellite phone. Once you put your phone in the case, you'll be able to make phone calls and send SMS using your own phone from anywhere Thuraya's satellites can see you, which is about two-thirds of the planet (granted, you're probably still screwed if your in the north or south pole). The SatSleeve measures 5.4 x 2.7 x 1.2 inches, and it weighs 100g, so it'll definitely add some bult to your kit, but it's the kind of thing that could have kept Gilligan's tour to three hours and left James Franco's arm attached to his body.
There's little to no setup involved, either; you attach the iPhone to the case, and flip a switch to activate it. Phone calls are then made/received through Thuraya's app within the phone, but the case itself has an emergency call button which will call a predetermined number and does not require the iPhone to be present. That's a very nice feature. The case will also act as an external battery, giving your phone a charge when the switch is flipped.
The one big, obvious hole? No data. It'll do calls and SMS, but no email, web, or porn chat. An iPhone just isn't an iPhone without that stuff. Still, though, it will transform it into a potential life-saving device. Without it, it's just a glorified MP3 player in the wild. Also, there's no such thing as free satellite calling. Thuraya's voice plans are 60p to £1 per minute for most places (which isn't bad), but if you're calling a remote location or another satellite network, it can skyrocket to over £5 a minute.
A SatSleeve with data will be coming in the third quarter of this year, though. That one will allow you to use all of your apps, email, all that jazz. Being able to download a map while in the wilderness (in case the one you're using turns out to be out of date) would be a really killer feature. This is probably the model you want to wait for. The voice-only version pairs via Bluetooth, whereas the version with data will pair via Wi-Fi. The data version will likely cost a couple hundred quid more.
For the time being, the voice-only sleeve won't come cheap; the suggested retail price is £330-odd. But if you're someone who finds yourself in the middle of nowhere with people to call, you may not find a better option.