It represents Google's response to other popular video calling options, including Apple's FaceTime, Microsoft's Skype and Facebook's Messenger.
It's not that different from the other video chatting services, except that it gives users a glimpse at who's making the call, helping people decide whether to answer or not.
Google says it's calling the feature, "knock, knock"
The new app, originally announced in May, is being released as a free service for phones running on Google's Android operating system as well as Apple's iPhones.
