Engineered with a focus on being incredibly fast, Duo lets users register with their phone number with the ability to connect a Google account (just like Allo), and then perform one on one video calls. That’s it. It’s meant to be simple, becuase it’s meant to be accessible to anyone and, again, really fast.
The only unique feature is that the call answer screen has the video call already started, so you can see exactly why someone is calling.
Look for Duo this summer on Android and iOS.