There were a bunch of "alpha brain waves" toys for a minute there a while back. A friend of mine had the Star Wars Jedi one where you put a device on your head

There were a bunch of "alpha brain waves" toys for a minute there a while back. A friend of mine had the Star Wars Jedi one where you put a device on your head and then it detects "alpha waves" and controls a small fan in a clear plastic tube that "levitates" a ball. We figured out eventually that you could pin the thing to the max by reading a book while wearing the device, you didn't actually have to focus directly on the ball.