Google just launched a new video calling app named Duo, which is designed to make high-quality video calling super simple across multiple platforms. There are plenty of other apps out there that already do this, but Duo has a leg up on the competition because of two features. Knock Knock allows you to preview calls from an Android device lock screen or the app itself if you’re on iOS. More importantly than Knock Knock, especially if you’re on iPhone, Duo makes switching from cellular data to Wi-Fi and back without dropping calls seamless. This is Google we’re talking about after all, so there’s a high probability they’ll be rolling out all kinds of cool new features in the future.