"What about the Thuraya SatSleeve? It is an adapter you plug your smartphone into to turn it into a sat phone."
The SatSleeve is a good idea, strangely implemented.
The SatSleeve is 199 grams with iPhone adapter - heavier than the standalone Thuraya XT satellite phone at 193 grams, and comparable to the Globalstar GSP-1700 satellite phone at 200 grams.
The SatSleeve also is a standalone satellite voice phone, with a speaker, microphone, but only one button. Without the iPhone, you can receive calls, and make an outbound call to one pre-progammed number (default 112). Without the iPhone or adapter, it's a 172 gram (6.1 ounce) satellite phone – pretty light!
When paired with your iPhone, you use the iPhone to send and receive calls and text – but no Internet access, despite Thuraya's relatively high speed Internet access - 60 kbps.
You can use the SatSleeve battery to supplement your iPhone battery.
Despite using Bluetooth for pairing, and having a flexible multi-piece design, Thuraya has not released an Android version. Android phones are outselling iPhones in most of the world. Maybe the Android market is too fragmented.
Too bad they seem to require your iPhone to be physically mated to the SatSleeve. Otherwise, you could have put the SatSleeve in a good location for a satellite call (e.g. outside your cabin) while your iPhone was in a good location for you (e.g. inside your cabin.)
You cannot use the SatSleeve for calls and text in North America, South America, Antarctica, most of the major oceans, and parts of Asia and Africa.