Speaking as a person that got to test the MagicBand, there crazy awesome...
Lets you into your hotel room by just waving your arm over a scanner, skipping lines for rides around Disney World, pay for your purchases with just a wave and there is a tracking chip inside that will follow you around and help protect your child if there ever get lost and even kidnapped.
This is going to be main stream in about a year or so where all guest will receive the band upon checking into the park. Below is a pick of what the band looks like and yes you will get to register it online so that you can keep the same one.