This pixelbot array could be programmed to form any of many thousands of displays. Each display would be capable of two functions: (1) presenting to the user data received from the large population of medical bots that roam the user's body; (2) conveying instructions from the user to that same large population of bots. The display could be activated or deactivated by finger tapping on the skin.
This is a step toward "e-glyphic" communication, an idea for Burroughsian nonverbal dialogue I've toyed with in several science fiction sketches. For a graphic depiction of dermal skin projection and its erotic potential, see my story "One-Hundred Years."