I love that you can see the self - winding movement of the watch through the clear circle on the face and also through the transparent back of the watch. (bedknobsandbaubles.com)
Sensors on the back of the watch face detect a user's pulse to track things like calories burned and distance walked or run. (fortune.com)
Each pixel on RetroShape's screen has a corresponding tactile pixel — or taxel — on the back of the watch face, allowing the virtual world to be extended to the 2.5 D physical space on its back. (sciencedaily.com)