by Diego Salgado/Laerte Strattmann/David Hunter: Diego Salgado/Laerte Strattmann/David Hunter

Cellphones don't offer much shade on a bright day. But in December, Philips Electronics filed a patent on a system that would allow the devices to help prevent sunburns and skin cancer. The plan integrates information about a cellular customer's location with real-time local data about how much ultraviolet radiation—the component of sunlight that can harm skin—is hitting the area, as measured by the National Weather Service or yet-to-be-installed sensors at popular outdoor spots like beaches and ballparks. The service would tell you, through a text message or audio alert, when to sunbathe, when to seek shade and how long your sunscreen will stay effective, all based on information about your location and skin tone and the type of lotion being used. "With the health importance of avoiding sunburns, this struck me as a positive application," says George Marmaropoulos, the Philips designer who invented the scheme. The company needs to find partners, but the service could be ready within three years