The Luxi incident light meter is designed for serious photographers. It is essentially an incident light meter that can be attached to an iPhone 4/4S or 5. For those who aren't avid shutterbugs, an incident light meter is used to measure light before it is reflected. The device is placed on the iPhone's front-facing camera and effectively measures how much light is hitting the person or thing you're photographing before it gets reflected off of them.
Unlike other iPhone photography accessories, the Luxi incident light meter doesn't try to turn your smartphone into something it's not (a high-tech camera). Instead, Luxi turns your smartphone into a photography accessory, aiding you when you're shooting with a real camera. Luxi has already reached its funding goal on Kickstarter and will retail for $24.95 when it's released in April.