no, no, no... it's definitely digital over GSM. Uplink has discontinued their analog module, and I think the Elk only supports the digital AnyNET anyways. Look, I know some people are worried about cell jammers. But don't you think when the technology is mature and widespread enough, someone will come out with WiMAX jammers too? Look, none of it is 100% foolproof, but cellular monitoring (as far as I can tell) takes care of 99% of the people who are likely to invade my home, i.e., crack-addicts and other small time criminals looking for a quick score who only think to cut the phone line. In fact, that's what heppened when my home was invaded last year; they only cut the phone line, but kept the cable line in-tact which was how my computer notified me of the problem.
GSM is a mature technology with an existing infrastructure, while WiMAX is still growing. All I'm saying is that for doing wireless digital communications, the two are equivalent, but cellular monitoring is mature and available today.