For a few years I was thinking about controlling the (un)locking and start/stop of my car via GSM. Two weeks ago, me and a friend of mine finally did it. Using a simple Arduino Uno plus GPRS Shield and Relay Shield we were able to call the Arduino and trigger a relay to open or close.
The proof of concept code of this simple setup can be found on github.
If you use the GPRS Shield of seeedstudio you have to know that the Relay shield can not be stacked together with the GPRS Shield because both use pin 7 and 8. What we have done is to connect pins 7,6,5,4 from the Relay shield to pins 2,3,4,5 on the Arduino/GPRS Shield.
WIth Sparkfun’s GPRS Shield you don’t have this problem because it uses pins 1 and 2 for communication.
