The Nether Machine/Reactor was added in the 0.5.0 update. This structure consists of gold and cobblestone blocks. The "real" Nether may not be added into Minecraft Pocket Edition due to performance issues, but as devices get more powerful we might see it. It may be added to modern devices. The Nether Reactor, when active, creates a massive tower out of obsidian (As of 0.6.0, it now spawns Netherrack) around it. It then spawns glowstone, mushrooms, sugarcane, glowstone dust, melon seeds, and other miscellaneous items, and Zombie Pigmen in groups of 2-3. The tower will slowly disintegrate, allowing you to exit if you do not have a diamond Pickaxe. If you mine the nether reactor core before it is finished, the tower will not break, thus freeing you of the need to fill the holes if you intend to make it your base. The Nether Reactor is not able to be created on the PC version and even though it is called the Nether Reactor it does not create Ghasts, Blazes, Magma cubes, or any other PC nether creature besides Zombie Pigmen. Also, the zombie pigmen's heads seem to be missing the outer layer of skin, showing only the skull.
You need the Nether Reactor Core which requires three diamonds and six iron ingots. You must then craft a 3 layer "Case" around the core in order to activate it.
After you build the reactor, hit the reactor core to activate the reactor. Once you activate the reactor,it will dig out a square 2 deep. Filling it with Netherrack. It is commonly belived that the sword is required to activate the reactor; while this is false, you should still have one in order to fight off the zombie pigmen.
The reactor remains active for about 45 seconds. After the reactor is deactivated, a Netherrack tower is left in its wake. The tower is approximately 18 blocks wide x 17 blocks long x 34 blocks high.
It should be noted that mobs can spawn inside the tower, mining should be done with caution.
It will turn night time once the nether reator "turns off."