Turn switch on and off with HVAC

I’m looking for a SmartApp that can turn a switch on and off when HVAC is on or off. Specifically in cooling mode.

Is there one available already? I can’t seem to find anything related.

How are you monitoring your HVAC system?

I’m sorry I should have mentioned that. It’s a variation of the CT50 with wifi. I added a zwave module to it a couple months ago and use the better thermostat app

I too would like to turn on a switch with HVAC running. Any solution for this?