Sending repeated SMS notification

I have a piston that watches the temperature of a greenhouse. Temperature equal to or greater than 70* turns on a fan and sends me a SMS message that the fan is on. Problem is that it will keep sending that SMS each time the temperature changes. Does anyone know how to limit that SMS to only once after the temperature rises to 70 or greater?

Post an image of your piston.

Also, best place to post webcore questions is on the webcore forum. There are several users who love to assist with building pistons…