For those of you interested in what might be a slightly lower level approach: I saw a talk from Andrew Trigell (of Samba/rsync fame) at linux.conf.au. In it, he was bemoaning the lack of Open Source firmware for radio transmitters, while pondering a UAV project hey were working on.
So, in typical tridge fashion, he and his friends created some, and given it is relatively simplistic, and the transmitters are quite tiny, the feature set seems pretty impressive (though I haven't had a need to use it... yet):
Tridge also happily uses an earlier version of OpenTX called er9x I believe. I've worked with him on a bit of the firmware you're talking about here, but it's not the same stuff. The most impressive thing about the SiK firmware you're talking about is the stupid range you can get from them on a good day; line of sight can be tens of kilometers (say 40+), and could potentially be used to communicate with satellites, all while using a max of 5W transmit power at 900MHz. There's plenty of more info on both the CanberraUAV and 3D Robotics blogs from him and others about both these topics. The following talk as LCA was about such satellites, and there was some talk about using these radios for these open source satellites.
So, in typical tridge fashion, he and his friends created some, and given it is relatively simplistic, and the transmitters are quite tiny, the feature set seems pretty impressive (though I haven't had a need to use it... yet):
https://code.google.com/p/ardupilot-mega/wiki/3DRadio