Thuraya is a regional carrier (as someone posted above) with really great service
within their coverage area and nothing outside of it.
I do believe that the SatSleeve has little adapters to accommodate different iPhone models (so you don't have to buy an entirely new SatSleeve each time you upgrade your phone, just the little adapter).
The nice thing about Thuraya is that their satellite phone service
runs at around 56k. Compare this to an Iridium
narrowband device (GO!, Extreme, 9555, etc) where they're running at 2.4k. With satellite
speeds 25 times faster than Iridium and Inmarsat narrowband, you can do some web-browsing and generally just have a better data experience.
Due to their regional coverage, however, Thuraya simply won't work
outside of the Middle East and Europe
If you ever find yourself needing a satellite phone
within their coverage map, the Thuraya Dual XT is a great choice as it is the only satellite phone currently on the market to offer satellite with GSM failover (or GSM with satellite failover, depending on how you look at it).