Thomas Reardon puts a terrycloth stretch band with microchips and electrodes woven into the fabric—a steampunk version of jewelry—on each of his forearms. “This demo is a mind fuck,” says Reardon, who prefers to be called by his surname only. He sits down at a computer keyboard, fires up his monitor, and begins typing. After a few lines of text, he pushes the keyboard away, exposing the white surface of a conference table in the midtown Manhattan headquarters of his startup. He resumes typing. Only this time he is typing on…nothing. Just the flat tabletop. Yet the result is the same: The words he taps out appear on the monitor.