I have been playing with an idea and some dremel rotary tools: Stainless steel mugs (cups) which essentially are just two layers of stainless steel with air in between. No seams, at least not on the inside. I got mine from the local gas station (they're trying to get loyal customers by selling "free coffee refill cups" for about $15, valid for a year at the time), but similar cups are available in a lot of places.

Anyway, my cup is a cylinder about 4-5 inches tall and just a tad smaller than 2 inches across. I did some dremel art and it turned out to something that may prove functional. Remains to be tested and verified.

The general idea is that the outer shell is a small fire chamber. The inner cup is for boiling, heating water and melting snow. The inner cup is put back into the outer shell when not in use, kept in place by friction created by a thick rubber band between those two layers. The inner cup retains about half an inch of the outer layer near the top, so I can put my mouth to it as usual. It even has the original drinking lid and handle!

Now the fire part - works, no mystery, but the overall setup is kind of fiddly. You will have to either support the fire cup part by rocks or suspend it beneath a branch (some thin steel wire rests in the void between those two shells for this purpose). The inner part will either rest directly on the outer part or be suspended. I've drilled a couple of holes for suspension in both parts. I've also cut a fire door and some ventilation slots in the outer shell. Around the cup I've wrapped some bicycle tubes (cut and glued to fit, this "ranger band" thing is a mystery to me). This rubber sleeve will keep my pack clean and is also backup tinder. And - the cup still looks and serves as an ordinary cup!

I'm assembling a small fire making kit and perhaps some other goodies to fit inside the cup - after all, it has a few cubic inches of space inside, and it is the logical place to put some fire making goodies, right?

Now all that remains is a) pictures, b) further field testing. The cup is small enough to fit a jacket pocket, sort of, and virtually ignored in a pack. I THINK this setup can turn out to be a nice and permanent part of my hiking setup, but further tests are needed.

The nicest thing about this setup is that - often you want to bring a cup anyway, right? Any chance of coffee? You bring a cup! Might just as well be creative about it... my little cup has some secrets..