I dont know much about GSM protocols. Can somebody here explain what might be possible applications for this thing? Would it be possible to decode recorded GMS calls around you? Is it significant vulnerability?
http://everything2.org/user/Jetifi/writeups/GSM
I don't think this is quite as big a deal as it's made out to be, since that A5/1 and /2 were both broken almost a decade ago, and most GSM providers have replaced these two ciphers with others since then. It might still be useful in places outside of Europe and the US though.
It's a motivated attacker attack. You have to be within radio range, and the attacker has to have specialized equipment and knowledge. It's not like an internet vulnerability, where one guy in Russia can exploit every single unpatched system in the world; this requires a bit of fieldwork. I wouldn't be worried unless you work for Apple, or something.