I have a GE Simon XT alarm system in my home and would like to have the alarm send me a text and/or phone call when the alarm goes off. GE has a GSM module for this purpose, but it is $250 and requires signing up for monitoring service. I don't see why I couldn't use the Arduino GSM shield for this purpose. The alarm panel has a readily accessible output that switches state only when the alarm is generated, so that gives me my interrupt/trigger signal. Seems like all I would need to do is monitor this signal in code, then have the Arduino board call/text me when it changes state. Anyone ever try this?