Mindball is a concept mentioned in a book I read in 2013 called Trying Not to Try. The game is usually played by two players. The players sit on either end of a table and a ball in the middle rolls away from the player who is more relaxed, focused, and meditative. If the ball reaches your end of the table, you lose.
Consumer EEG sensors and chipsets have become cheap and accessible enough to use in experience design projects like this one.
See the Github