From Repair Mobile

You are better off with GSM for Telemetry

I'm sure there are those who will disagree with me, mainly the telephone companies who provide pstn lines and the telemetry equipment manufacturers who are still struggling with the changes they need to make to embrace the mobile phone (GSM) network, but in my mind there is no reason to even dwell on this decision. Chances are that you are fitting telemetry onto a customers site, whether it be domestic or industrial, so you either get a new phone line installed or you piggy back onto the existing one. More details [1] - thanks to toolbox.com