I recall reading in the book "Takedown*" that this was the method that convicted cracker Kevin Mitnick used that let the feds right to his door. Coordinating with the FCC, FBI and several cellular companies they narrowed his location down to an apartment complex in Raliegh, North Carolina February 1995 where he was arrested.

Running a modem session over an analog cellular connection has been known to be quite unreliable due to static, background noise and geographics among other things. And having repeatedly dropped calls left quite a large series of footprints for the investigators to follow.

Using their direction-finding equipment had it's limitations. Apparently they could only listen to a conversation at the site of a cell tower, as they were tracking the transciever of a cellphone they were listening to by the breaks in conversation. The other party broadcasting from the tower was one that Tsutomu Shimomura recognized, the voice of Eric Corley. At that point, they knew they were close. Also the fact that dropped calls were common was one of the frustrations that the feds experienced while narrowing his location down.

The moral of the story, k1dd13z, is that it is not very wise to use cell phones for illegitmate purposes, as they are becoming more and more like homing devices since manufacturers are now including assisted GPS technology for E911 services in them as well. (then again, when do crackers use those few braincells they have for any common sense anyways?)

* Book Title: Takedown: The Pursuit and Capture of Kevin Mitnick
Author: Tsutomu Shimomura with John Markoff
Publisher: Hyperion 1996
ISBN: 0786862106