You know, we are not that far off from having a suitable, portable "fuel cell" that works much like a catalytic element. In fact, what's so wrong with catalytics? Maybe we just need to find a reasonable way to isolate and protect the heat source so that the chance of it igniting an external flammable are next to nothing.

I've been so cold in my wall tent (read big canvas tent) that I've had to light off all three propane burners on my BIG cookstove, plus a hot fire in my woodstove. That's 12' x 17' in a good blizzard. Eventually it got warm enough in there that I could get outta my FWG and do some cooking. Ah, now that was living. I believe that was the night I made beef stroganoff and fresh scratch sourdough fritter rolls and triple berry compote topped with yogurt... Oh God, I miss elk camp.

If you can keep the airflow down, you'd be surprised I think at how much heat you can get out of one candle in a jar. The trick is to trap the air. Not an easy proposition in these new fangled tents.

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The ultimate result of shielding men from the effects of folly is to fill the world with fools.
-- Herbert Spencer, English Philosopher (1820-1903)