first of all, a great howto - thanks a lot!
My project would be: to open my garage by a simple phone call, using a pi and a usb modem.
Do you perhaps know what I need to doe here? Receiving calls and checking IDs is simply done by AT commands? How can I tell if a call is about to happen, I mean how to recognize if a ring the modem? Do I have to poll something constantly, or is there a trigger somewhere when the modem rings?
Thanks a lot in advance!