The Rock 7 RockBLOCK is a fascinating communications module that gives TTL-level devices like Arduino access to the Iridium satellite network. This is a big deal, because it means that your application can now easily and inexpensively communicate from any point on the surface of the globe, from the heart of the Amazon to the Siberian tundra. This library, IridiumSBD, uses Iridium's SBD ("Short Burst Data") protocol to send and receive short messages to/from the Iridium hub. SBD is a "text message"-like technology that supports the transmission of text or binary messages up to a certain maximum size (270 bytes received, 340 bytes transmitted). Written by Mikal Hart with generous support from Rock 7 Mobile. For more information, visit the Rock 7 http://rock7mobile.com.
See also SparkFun's fork at https://github.com/sparkfun/SparkFun_IridiumSBD_I2C_Arduino_Library.
Chaos at 99,000 feet: a balloon tracked by IridiumSBD bursts in the stratosphere