Just like the name implies - a machine that will disassemble a block or an item down to its components.
it could be made so that it breaks down an item down to its "raw components" or down to the components it is made of
e.g. an extractor could be broken down to its initial components - circuit, machine block, tree taps; or if down to raw materials circuit and machine block will be grinded down as well, yielding iron, wires, redstone and wood(or sticks)
It wont be 100% efficient of course, but it could be made upgradable.
Right now, if you make a low tear network of generators(e.g. :Water Mill: ) and machines, the only thing you can do to them, after you make smth more efficient, is recycle them for scrap or store them in a chest. I believe it will be nice to have a machine that will allow you to actually recycle some machines and salvage some of their parts for another use.