relay message to peripheral devices

Hi, I am new to arduino. I want to build a simple device based on arduino gsm shield. The idea is an arduino running on batteries and giving kind of relay signals to some other devices to toggle them on and off which are connected to some ac supplier. That why only when it is required the peripheral devices will use power. So an ardunio Gsm shield which would be able to accept a call or sms from a known number with some logic of identification (not important here), and then let other devices consume power. Is it possible? I want to use off the shelf devices like fans etc. to be able to get a relay message from arduino. Is it possible or do I have tinker with devices?

Thanks.