I would like to build a 2 way radio system that uses internet protocols instead of standard radio waves. Each "radio" would have a SIM card for wireless internet access and upload / download audio from a web service. Could this be done? My main concern is the processing power of an Arduino. I've researched Netduinos as well but there doesn't seem to be a stable, known solution for interfacing to a GSM shield. Any thoughts?
Can't get head and tail from the name of the topic, GSM standard works "Over_The_Air", in other words radio based. If you want something different, that works over i-net, it's VoIP based. Unfortunately, arduino can't compress/decompress VoIP protocol real-time. IMHO, the minimum grade of CPU should be Cortex3, Maple board, Discovery, etc. Project complexity definitely not "for beginners".