https://www.theverge.com/2017/11/7/16619124/warby-parker-iphone-x-app-face-mapping-glasses

The iPhone X has only been out for a few days, but we’re already seeing people take advantage of the face mapping technology on the phone in numerous ways. Some, like Animoji karaoke are more entertaining than useful, but others — like Warby Parker’s new app — are a little more useful (as spotted by Joanna Stern on Twitter.)

The glasses company is cleverly using the iPhone’s camera to take maps of people’s faces, and use that data to recommend styles of glasses that will best fit your face. It’s a step beyond the digital try on system the company has previously offered, where it would try to place a virtual pair of glasses on a picture to let you see how it looks.