I always like playing around with Google's latest apps. They released a new one today called Duo that aims to make video calling between 2 people (and for now, only between 2 people) super easy. The app is basically one button (to start and end a video call) and has interesting features, most notably the "Knock Knock" feature which lets you see the caller and what they're doing before you even pick up the call (translation: before they see you).
Some people are billing this as a FaceTime killer but I'm not so sure just yet. It is very easy to use but my initial reaction is that it wasn't going to make me quick to switch over any time soon. We'll see how this pans out for Duo though.