I have a hard-to-heat room over the garage of my house. In winter, that room is always 2-5°F degrees colder than the rest of the house. I tried to adjust the central forced-air heat flow into the room, even adding booster fans, but keeping the room warm remained a problem. So I added a supplemental electric space heater.
Companies sell programmable thermostat controls for gas fireplaces, which come with a handheld remote control, so I decided to adapt one to work with my space heater. The controller that would normally go in a gas fireplace provides a low-voltage, low-current output to turn the fireplace gas supply on or off. I decided to use this output to drive a power relay that would control my electric room heater. The remote receiver uses batteries for power, but because I have AC power already available for the heater, I eliminated the receiver batteries and use a power supply instead.
Although the concept of remote temperature doesn’t seem particularly innovative, I did not find anything comparable available for sale that was portable, remotely controlled, and programmable for temperature control. This gadget meets my needs very well. Now I enter a comfortable room in the evening while conserving power the rest of the day. And if I want to adjust the temperature, I do so from the comfort of my easy chair.