Kelly Kettle Boiler
We can't say enough about this product. Small enough to pack along on hikes or for camping, it can boil (and therefore purify) water in mere minutes using nothing more than twigs and whatnot you can find anywhere. The model we have here, The Trekker, is the smallest available and it boils .6 liters -- enough for two cups of coffee, two or three bowls of oatmeal, or a backpacking dehydrated meal in a bag.
So whether you're looking at it for camping and hiking, or as a preparedness item, you can see the value of having one. Limitless fuel means limitless water purification and limitless cooking -- quickly and easily. It's a water AND cooking solution in one. The design is basically a rocket stove. All the elements of one are there: limited air intake for drafting, a hollow "chimney" to contain the heat and draft air, and the water acts as the insulation to further contain the heat.
It takes a second to wrap the mind around how it works, but once you do, it makes perfect sense. The water is housed in a hollow compartment sort of like a bunt pan. This increases the surface area which the fire can heat, speeding boiling, plus increases the heat flow due to the rocket stove-like effect it achieves. Just a great product. Stainless steel construction for durability. We will not even bother carrying the aluminum version. . .it's not much cheaper and stainless is just so much more durable and less toxic.
The video here is one we shot using our Trekker. . .