The glass on your smartphone screen doesn't do a lot right now: it lets pictures and touch input get through, and that's about it. It may pick up a few extra talents in the future, though. Researchers at Polytechnique Montreal have developed sensors that can sit under the surface of the scratch-resistant Gorilla Glass used in many mobile devices. Their approach etches optical waveguides into the display, letting it track changes in light. As a result, the screen can do things that would normally require either wiring or dedicated sensors. Your phone could check its temperature using light, and the manufacturer could even embed a unique optical pattern into the glass that lets the phone identify itself; it might get much harder to clone a device (and, presumably, its information).