Americans' chances of getting skin cancer are 15 times higher today than 60 years ago. The reason? Increased exposure to ultraviolet radiation (UV) caused by thinning of the ozone layer. A new product may help people beat those odds. Developed by physicist Ori Faran at Technion-Israel Institute of Technology, the Sticker measures the body's accumulated dose of UV, warning its wearer when to get out of the sun.

Photochromic elements in the Sticker change color as they absorb UV. By varying the concentration of these elements, Faran has produced versions for a range of skin types. When the Sticker turns red, apply more sunscreen; if it hits orange, it's time to go home. Skyrad, a startup incubated at Technion, plans to introduce Stickers in the U.S. next spring. Each single-use Sticker will cost 10 to 20 cents.