As tital describes, is there a way to trigger a smart plug which has a heater connected to it when the temp drops below set temperature?
Yup, via Automations in the new app. The “If” would be temperature sensor condition to be monitored, and the “then” would be the device to control on/off. Here’s an example I quickly put together to help illustrate:
Obviously you’d have your own sensor capable of detecting temperature, and your outlet, but you get the point that it’s doable in ST without any custom smartapp.
All that said, please keep safety and fire hazards in mind when automating things like space heaters!
You need to make sure you are using a smart plug that is rated for the amperage of the heater too.