Detecting Phone Snoops

"Google can tell if someone is looking at your phone over your shoulder":

Google researchers Hee Jung Ryu and Florian Schroff will present a project they’re calling an electronic screen protector, where a Google Pixel phone uses its front-facing camera and eye-detecting artificial intelligence to detect whether more than one person is looking at the screen. An unlisted, but public video by Ryu shows the software interrupting a Google messaging app to display a camera view, with the peeking perpetrator identified and given a Snapchat-esque vomit rainbow.