Seemingly going after Apple's FaceTime, Google has unveiled Duo, the tech giant's latest foray into video calling. What makes Duo very unique is the fact that it only does one thing, but it does it extremely well.

Duo, which was officially launched for the Android and iOS app stores on Tuesday, is Google's simplest video messaging app. Even its name, Duo, signifies the tech giant's desire to keep the app exclusively for one-on-one video calling.

There are no fancy filters, no sparkly stickers, and no option for group calling. In fact, Duo users do not even need a Google account to use the app. The app automatically activates through a user's SIM card, and it initiates a call directly from a smartphone's contact list.

What Duo does, however, is something that its closest competitor, FaceTime, cannot do. Duo enables direct video calling among both Android and iOS users. FaceTime, on the other hand, is exclusive only to Apple users.

What google has essentially done with Duo is to create a product that excels at one thing. That one thing, however, is polished to perfection, as proven by early tests of the app.

This is not to say that Duo is absent of any bells and whistles, however. The app does have a couple of very notable features, the first of which is called "Knock Knock." His particular feature allows users to see a video preview of the person who is contacting them even before they answer the call.

Knock Knock serves a dual purpose. On the one hand, it gives users a pretty novel experience, and on the other hand, it enables users to seamlessly answer the call. Thus, with Duo, the days of asking the person at the other end of the line if they can see and hear the call seem to be at an end.

What's more, Google also promised that Duo would be able to seamlessly transition between Wi-Fi and cellular networks. During initial tests, the video feed just freezes for a second or two, before continuing again. The audio feed was largely uninterrupted.

Duo is one of two apps that Google has announced earlier this year. The other app, Allo, a dedicated messaging application, is set to make its debut soon.