I remember my father occasionally putting lunch items on the car engine to heat up when I was a kid. He had stories of heating meals that way during WWII. One summer we drove a newly restored '52 Hudson Hornet across country. Being frugal as he was, most of our meals on long driving days were from cans of soup or other items held to the engine with bailing wire. We didn't have any explosions but were always careful to place canned items on cooler areas where there was less risk of exploding.
The manifold oven brought back memories of that trip.
it also looks like a good way to reheat your tactical bacon while fleeing the zombie apocalypse.
http://www.thinkgeek.com/product/c399/
This probably isn't recommended when back country camping unless you're chumming for bears.
