I've seen reports of teaching monkeys to play computer games with a joystick and a wired helmet, and then disconnecting the joystick, and they keep playing the game with their brain only. This has recently been done with people, too.
Now it has a clinical application in Britain. They put a special helmet on a kid with ADHD, so the kid can play a computer game with just the mind 3 times a week for 12 weeks. The kid really has to concentrate to make the game work, and they said it reduced impulsive behavior. I have no way to evaluate it, but if it works, cool.
The system is called Play Attention. They're planning to roll it out across the UK this month.