I noticed that acoustic fire extinguisher some day ago...
Pretty interesting but I find it's application is questionably. When it comes to protection - prevention and cleaning up after natural disasters, such as forest fires (or any other fire of a larger magnitude for that matter) we should take into consideration the magnitude of these problems...
We should think much bigger - an efficient device that could cancel out a whole forest fire... Maybe some high-frequency EM wave that will excite the oxygen in the air above say, an acre of land, so it cannot join with other elements (oxidize them - ignite) and thus disable any burning and flames. This would be like suddenly placing all this flammable material in a vacuum.
Of course, this would not be practical in every case, since ionized air can be toxic and even lethal to humans. Maybe ionization was a bad idea, but I am hinting towards a similar process that would reduce the reactivity of the oxygen in the air. Maybe release a non-toxic chemical or some sort of sub-atomic particle that would 'saturate' all or at least most of the available oxygen.
Note that ionized air (the ionosphere:
http://en.wikipedia.org/wiki/Ionosphere) blocks of some radio-frequencies, but I believe for a few minutes (until the flammable material cools) it would pose a problem. Also note that, oxygen in the form of trioxygene (O3) might form as a result of such 'extinguishers', which is no good. It is also very unstable (as a molecule) and breaks down to O2 (at given pressures).
O3 makes up the Ozone layer of our planet -
http://en.wikipedia.org/wiki/Ozone ... O3 is very rare in the troposphere, this is because, as said previously, it breaks down to O2 in the lower layers.
The purpose of this reply was to point out some facts (interesting or not) and some similar concepts to the project Art shared with us - what problems could arise, criteria, side effects etc. Now, if nobody else minds, I believe we should not waste a good topic and get back to discussing how to imagine the unimaginable. Or, is it really unimaginable?