The Reiff system is what John uses on the factory birds when pre-heating is needed.
My Arizona acclimated 912ULS does not enjoy starting much below 50 degrees. I do have the old style starter though and the newer high torque/speed starters might improve this.
There are days here that pre-heat on my particular engine would be beneficial. The Reiff system would be perfect. Problem at my over regulated airport is we can not leave anything plugged in and operating while not in the hangar. No heaters, appliances, tools, battery chargers ect.
Just the fridge.