A cheap way to remotely communicate with an Arduino is hard to come by. This hack uses a $15 cell phone and a 3/32” stereo connector to accomplish this task. It turns out to be significantly cheaper than buying a full out shield.
I wrote a lightweight open-source library to handle the GSM communications allowing the user to send, receive, and read text message as well as check battery
and signal strength.
I have been excited to get dozens of emails from people all around the world using the library, many who were embarking on their first Arduino experience.