@tslagle13 already has an app to change the mode on the thermostat based on temp. The app he wrote can use any temp sensor, internal or external. For my house, that app made more sense than a scheduler app like you’re doing. Here’s a link to the post where he told me about it:
If nothing else, it should give you an idea about how that kind of coding works.
Edit: Sorry, after a re-read that may not be what you’re looking for…