Wearables need to be small. That way, they use less power, take up less space, are less intrusive, and are more convenient. However, “small” is a problem. How do you control the devices? Tiny buttons and dials can be awkward (if not impossible) for many users, and touchscreen displays are so small that it’s difficult to be accurate with a typical finger touch. This is one reason why researchers are turning to voice or gesture or other means of control.

A group at the Carnegie Mellon Future Interfaces Group have developed the LumiWatch, a research project that demonstrates how a user’s arm can be converted into a touchscreen. Fitting in a typical smartwatch package, the system manages to conquer several tricky problems. It incorporates a pico projector that displays an image on the wearer’s forearm. An array of sensors is able to detect 2D position information for a finger touching the skin on the arm. That alone would be impressive, but the system also calculates the geometry required to display the image on the arm with the correct aspect ratio, in spite of the curved surface. Most important of all, the device incorporates all the computing power and memory required to perform all these tasks.

At this point, the LumiWatch is simply a technology demonstration, but it points the way to providing more space so that users can control small wearable devices. This could change how we interact with our wearable devices in the future.