There are some apps that look like they might do what you want in the official smart set up apps. These are the ones that are already available for quick installation from your smartthings mobile app.
Take a look and see if any of these fit. You would need to have a Smartthings connected temperature sensor in both zones. In particular, “keep me cozy two” (#3 in the Green Living section) might work.
As far as devices, you’re likely okay with your gas heater, but underwriters laboratories and most fire departments recommend never putting a space heater on an unattended mode. Those things just cause too many fires to run remotely. But there are many other good use cases for a zone to zone comparison.
