Sylvain Munaut was presenting on Wideband GSM Sniffing at the 27th annual Chaos Communication Congress, where he was using a series of four phones running OsmocomBB as a GSM packet sniffer.
The slides are available from http://events.ccc.de/congress/2010/Fahrplan/events/4208.en.html.
A preliminary video recording (simple dump of the stream) can be found at from this mirror
Please note: This talk was using a lot of custom software that has not been released and is not part of OsmocomBB. For more details, read this mailing list post by Sylvain Munaut