I've looked at these a few times, considering whether or not tit would be feasable to turn one into a hobo type stove. Haven't seen one in the flesh tho, so keep holding off.
Yes, to your question, they were designed as lunch boxes in India and are gaining in popularity again.
Simon
I have recently bought a set of these and I really can't see any way that one of these can be converted to a stove, there is a metal strap around the bottom can and all the cans are solid so i can see that either the food will burn or the entire contraption might explode (COOL!!!).
I think that they do a sterling job of transporting hot food but I don't think that there is a way to cook in them.
Of course I am aware that you lot are an imaginative bunch so I guess that someone will come up with a way to add a cooker on a strange contraption to get a brew!!!