Here's a video from AimPoint instructor, Stewart Craig. He is showing the Focus Band in action while a player is using a conventional green reading method versus the AimPoint Express.
Granted, I do not know much about the Focus Band at this point. But, I did study learning and the brain periodically when I was in college. From what I gather, the Focus Band is measuring the right brain vs. left brain use. And when you're using the right side of the brain, the brain is more 'calm' and is using more feel and senses than the analytical, left side of the brain. I would imagine that part of the 'goal' is to transform the analytical left side of the brain function into more automatic, right side of the brain use over time. For instance, a person learning to juggle will use the left side of the brain heavily. Once they start to become more natural at juggling, the right side of the brain is used.
What's interesting about this video is that it shows AimPoint using the right side of the brain and really calming down the brain whereas the traditional green reading method uses more of the left side of the brain. That's a part of the beauty of AimPoint Express, it appeals more to the senses and feels.