The Google Phone app is gaining even tighter Duo integration allowing one to directly make Duo video calls from within the dialer. While the Phone app previously showed Duo video calls in the call log list and allowed one to switch from a voice call to a Duo video call, the addition of this button makes the integration complete in many ways.
It was previously possible to directly start a Duo video call from the Phone app, but for that, one had to tap on the contact and then select the Duo option. Now though, the Google Phone app gets a prominent floating Duo button that sits right above the dialer button in the 'Recents' tab. Tapping on it will open the Duo app from where one can make a video call.
Many other Android OEMs have also integrated Duo in their Dialer app. Samsung, for example, already offers an option to initiate a Duo video call when one enters a number or opens a contact in the Phone app.
The new Duo button in the Google Phone app is available on non-Pixel devices as well. As of now, the button is a part of the latest Google Phone beta app (v50.0.314411800).
Source: Android Police