Google seems to be in the process of readying a pause button for its Duo mobile video chat app. This is based on references found within the app during a teardown of the most recent version (v37.0) of the app by Android Police. As this is not an announced feature, nor one that is greatly explained through the limited references, it remains to be seen when it will arrive, or the exact extent to its functionality.
That said, the principle behind a pause button is unlikely to need much explaining. As Duo already allows users to mute sound temporarily and this pause button assumes the same will soon be available for the video feed in general. Thereby allowing Duo users to temporarily pause the video so those on the other end of the call can't see. Ultimately, an easier option than the alternative – ending the call. While the pause button seems likely to be on the way, it remains unclear as to whether activating it will both mute the audio and turn off the video, or just pause the video allowing the audio to remain connected.
In addition to the new pause, it also seems likely Google is preparing to embark on a new campaign to attract more users to its Duo service. More specifically, it would seem Google is planning on recruiting current users to help convince their family and friends to also start using the service. If the feature pans out as expected, then this will arrive as a rewards system where current users will receive a referral award each time a new person is added to the Duo list. At present, the details on this are very limited and so the fundamentals of the program remain unknown. For example, it's not clear whether current users will be rewarded by only convincing others to download the Duo app, or whether the other person will be required to initiate a Duo call before the reward is given out. Likewise, the actual rewards themselves remain relatively unknown. Although, there is the suggestion Google Play credits may be part of the equation. As is always the case with app teardowns, there are no guarantees that either of these features will actually end up as user-facing features, or whether they will arrive as initially expected.