How do I collect redstone on iOS?

Solution 1:

The iOS version of Minecraft currently doesn't have Redstone items programmed into the game (if you go into Creative you won't find them), so breaking the ore will simply result in nothing dropping. You won't be able to collect any Redstone Dust until the game is updated to include the item.

Solution 2:

Mojang announced a new version of Minecraft PE today. When this version is approved, Redstone will be added to creative mode, although they haven't mentioned if it will be functional as it is in the desktop Minecraft.

There is no Redstone in survival on PE, and no word on when it will be added, sorry.