This is a new item that can possibly added in the new 0.5.0 update which is not yet ready to publish. This Mahine, as Johan Bernhardsson says, will consist of iron, gold, and diamond. This item is said to spawn zombie pigmen, mobs that originally came from Minecraft on the PC. The "real" Nether will not be added because of performance issues. This Machine will supposedly act as a dsipenser and will spit out special nether features.