I have bought this sim900 GSM module: http://www.netram.co.za/New-Products/SIM900-GSM/GPRS-Minimum-System-Module.html
I am a little stuck thou, i can send SMS's, call people, receive sms's and get all the gsm serial info i need but i would not know where to start when it comes to creating something that i can control with an SMS.
Basically what i am wanting to create is something that will read my SMS and either turn PIN1 on or off or PIN2 on or off or ETC.
I am wanting to use it as an immobiliser so i can send an SMS to the module and turn key components of my vehicle on or off.
any help will be greatly appreciated.
thank you for any assistance 
If anyone has any idea what i can do, please could you advise me, i would really appreciate this
Basically what i am wanting to create is something that will read my SMS and either turn PIN1 on or off or PIN2 on or off or ETC.
If you are able to receive SMSs, this should be trivial. Post an example of an SMS that you are sending to the Arduino with GSM shield.
I know this should be simple but i wouldnt know where to start unfortunatelly. any help would be appreciated, thank you