[dmix]

There are also IMSI Catchers intercepting GSM all over the USA, for example this twitter feed reported one at SFO airport recently:

https://twitter.com/cellhacking/status/524562944928264192

And all over Washington DC:

https://twitter.com/esdamerica/status/512293117052334080

[larakerns]

There are now a few Android apps in development to keep track of the towers your devices use day to day to hopefully detect rogue IMSI catchers.

This one is the most promising: http://signup.spideyapp.com/