As of version 0.13 redstone was officially added to Minecraft Pocket Edition. But it’s still in its early stages of development and this means some features are missing. Redstone + is a mod which tries to make those features available for us right now. So far the mod features include repeaters, pistons, the command block and a slime block. Dispensers, droppers and redstone comparators are still a work in progress but hopefully something we will be able to use soon as well.