Bat Nets

This item would be pretty basic, you right-click it on a bat to catch them (it may seem way too hard, but you can use potion of slowness to make it easier). Once you catch a bat you can release it. Also if you release the bat, it won't despawn.

You may be asking "Why would anyone need it?", but bats are actually used for redstone-circuits. You can create awesome randomizers with it.

It would require 5 strings to craft.