So I've never really worked with Items in Minecraft before, and I'm pretty confused.

 

I want to make an item where I right click on a Controller block and then right click on all the blocks the Controller will operate. This would require somehow storing a BlockPos in the item; and I'm not even sure if items get their own instances (like TileEntities), or if they're just designed to handle logic (like Blocks).

 

Anyway, whats the simplest way I can do this?

Store the BlockPos in the item's NBT and read it when right-clicking.

If using 1.9+, you should be using the Capability system instead of interacting with ItemStack NBT directly.

 

The reason you need to use NBT / Capabilities is indeed that unlike TileEntities but similar to Blocks, Items do not have unique instances so you cannot store any mutable data in the class.