If each heating unit can be turned on or off individually by “unplug” or “plugging in” the unit, then this should be do able… a little complex, but certainly doable. The important part here is the ability for the heating unit to be in the ‘on’ position when it’s first plugged in. Many things ‘default’ to off when they are first plugged in. Using a high amperage relay or outlet you will be essentially unplugging and plugging in the unit so you need to verify that it will be “on” when power first goes to it.
After that it’s a matter of having a temp sensor in each room that you want to control, as well as a motion sensor in each room you want to control with presence.
Then a simple program should be able to be written (if it hasn’t been already) that turns on the unit when the temp sensor reports below X and then off when the temp sensor reports above Y.
The motion sensor part makes it slightly more complicated, but still doable. Probably what I would do is write the program with a variable for high and lows. When the program starts it’ll initialize those for variables for “no one is in the room”… for example, it’ll make the variables 65 and 70. Then when the motion sensor sees motion, it changes those to 70 and 75. When motion stops, they are changes back to 65 and 70.