Heat in a can
Fancyheat
I just found these items at a nearby store, they are used for heating food for banquets and such. They are called "Fancyheat" and they are in a tin that can be resealable and last at least 2.5 hours...
Would it be worth carrying one? It is about the size of two tuna fish cans stacked on top of one another. I bought two to test out, they were 69 cents a piece, figured it could hurt, in a pinch they could be used to boil water and provide a little heat, and after its all used up you could use the can for something...