Source: http://people.csail.mit.edu/wli/blog/thi...

The Eone Timepiece has two ball bearings in two circular tracks so that you can use your sense of touch to know the hour and minute of the day. Underneath the watch face, magnets cause the ball bearings to move, much like analog watch hands, to the correct hour and minute positions.

It's a watch "designed for everyone": It was created in close consultation with people who are blind or have low vision, but it is meant for anyone who has ever wanted to known the time when it isn't possible to look down at your watch or phone. I'll be the first to admit to I've used it to check the time during meetings. :) More accurately, it's not a watch, because you don't need vision to tell the time; it's a "tactile timepiece."