I have no problems believing you can induce a tactile stimulus with a modulated voltage; it's way too easy to experience that by mistake. What I don't get is how it's supposed to work without a touchscreen: I believe that, in order to provide the appropriate feedback, the device needs to know where the user is touching, and with good accuracy; yet, in most of the applications it's not obvious where they're getting that information from.
If the device works as advertised, it would constitute a major breakthrough in augmented reality, well beyond tactile feedback, as it would turn pretty much anything into a touch surface.
@Richard.Hein: A robutt. Classic argument about mandatory spellcheckers.