If over the horizon satellite communications are a requirement you are in luck! An Outback Challenge team from Holland just helped you out.
For participation to the https://uavchallenge.org/
medical-express/ the http://mavlab.tudelft.nl/ team had to design a cheap and light weight iridium satellite communication module for there www.delftAcopter.nl.
As there is huge interest from the UAV community in using light weight and reliable satellite communication the http://mavlab.tudelft.nl/ made the iridium development open-source so the UAV community can benefit from this achievement.
For the opensource hardware and software see: