For this inquiry of yours, it will be best to do it with the use of I/O Juggler, where the action will be to send SMS when there are changes to the relay status. But for the second SMS you are pointing out, I am not able to grasp your idea. Do you mean you want to trigger the RUT955 Relay when you send a certain SMS? If this is the case you can create a new rule for SMS where you can activate the relay or deactivate it.
Like what is shown in this image:
I hope this helps