> Beepers as surveillance devices, rather than the drug
> trade itself was my starting point.
I'm sure that there's a cross-over. I've seen software systems, mostly hawked to intelligence agencies but I bet plenty of big-city drug enforcement groups have them, that will perform cross-correlation on phone calls, cell phones, beepers, whatever kinds of communication you can find. Using a pay phone doesn't help you; catching drug dealers using common technology is a whole lot easier than catching spys.
/jordan