Google just released Duo for Android devices in Canada (iOS version is expected to follow shortly). Duo is a simple 1-to-1 video calling that takes the complexity out of video calling. All you need is your phone number and you’ll be able to reach anyone in your address book. No separate account is required, so you can sign up in just a few steps.
Google says that Duo is fast and reliable, so that video calls connect quickly and work well no matter what network. Call quality adjusts to changing network conditions to keep you connected. For video calls on the go, Duo will switch seamlessly between Wi-Fi and cellular data automatically without dropping your call.
Knock Knock makes every call feel more like an invitation rather than an interruption, allowing you to see live video of the caller before you answer and get a sense of what they’re up to. Finally, Duo was built with an emphasis on privacy and security and all Duo calls are end-to-end encrypted. Duo looks to be as simple to use as Apple's Facetime video calling app but has the advantage of being cross platform. Duo can also be seen as competition for Skype and similar video calling applications.
In order to use the service/app both phone will need to have the app installed. System requirements for Android phones Jelly Bean and higher, and iPhones with iOS 9 and higher.