(Heater)
A simple stove can be made by placing a plant pot upside down on top of a candle.
(Newspaper)
Putting rolled up newspapers inside a sleeping bag will keep you warm.
This is a cold proof idea that could be used in times of disaster.
(Rain coat)
It will be cold proof if you wear it inside.
(Heat pad)
If you put it between the shoulder blades, you can easily warm up your body because of thick blood vessels in between the shoulder blades.