The GSM module can communicate with any other devices using two pins RX and TX. The data is sent or received serially through this pin. The data is nothing but AT commands which the GSM module can understand. You need a programmed device to make use of these pins.
Apart from this pin the GSM module has a speaker out which you can use with dtmf decoder to control the relays as described in that project.
YOU BETTER USE A CELL PHONE other than the GSM module since there is no microcontroller in your project.