Sun damage is no joke; the warmth feels so, so good, but ultraviolet (UV) radiation from those rays is responsible for a whopping 90% of non-melanoma skin cancers. In order to educate about the dangers of overexposure, the cosmetics pros at L’Oreal and La Roche-Posay went high-tech with My UV Patch. The stretchable sensor affixes to skin and lets users know when they’ve had enough of the bright stuff. After applying the heart-shaped sticker to a body part they’d like to monitor and going outside for a while, users can take a snap and upload it directly a custom mobile app that gives a real-time analysis of exposure, thanks to photosensitive dyes that change color in daylight.