I've always wondered if it's possible to use a very powerful magnet to remove nails from lumber? I'm sure that the magnet would have to be a really strong electro-magnet, such as the ones they use to lift cars at auto junkyards.
However, if this is possible, it may not be something that should be exposed to the public, because it could become a weapon. In other words, someone drives up to your home, activates the magnet, which removes all the nails as well as steel plumbing, metal electrical boxes, your appliances, and so on. This, in a matter of seconds, your home would be nothing but a pile of lumber, with all your (non-iron) furnishings buried in the pile, and all your iron metalic furnishings as well as all the nails from your home, leaving the scene by some crook.....
And, dont forget, your belt buckle is metal. Say goodbye to your pants!!! :)