What are you looking to keep heated?
My usage is to keep a well pump house warm when we have freezing weather.
I have a cheapo small space heater with its own thermostat but for some reason I can never get it to turn off properly.
So I saw that Meross outlet noted above but decided to give a more low tech option a try first.
A Heatit thermo outlet.
Thermostat controller outlet
www.amazon.com
It's specifically made for my use. It's thermostat turns the power on at 38F and off at 50F
I got the model with 2 outlets. I plug the heater into one and a red LED into another. The led is installed so I can see it from my house to know when the heater is on.
Works well so far. This is the second season.