For over 70 years, during winter in Alaska and Northern Canada, the Herman Nelson flameless pre-heater is employed to assist in starting aircraft that have been cold soaked in extreme cold temperatures. Two models I've seen are either diesel/kerosene powered or avgas powered. The heaters are often mounted on skis/skids. The Herman Nelson is also used by Canadian based Kenn Borek Air in their Antarctic operations.
Below is a photo of a sled mounted Herman Nelson heater, warming a Superior Airways Beechcraft Model 18, (ex RCAF C-45 Expeditor),:
