Owners of Chromecast and Android TV devices can now use Google Assistant on an Android mobile phone to control content. It is not quite clear when this feature first became available, and it is also not currently clear if it is available to all users. However, for some at least, the functionality is now live.
Which now means if you own Chromecast or an Android TV device, you can pretty much control the unit in the same way you can with a Google Home, irrespective of whether you actually have a Google Home unit or not. So for example, when launching Google Assistant on a mobile phone and telling the Assistant to play a video or a song on the Chromecast or Android TV device, the Google Assistant will comply. Likewise, once content is being played on a device (and providing the action was initiated via the mobile version of Google Assistant) then you can contextually ask Assistant to perform other actions. Such as "skip this one," "turn the volume up," "close the application," and so on.
While it remains unclear how widespread this feature is, it does seem to work with any Chromecast and Android TV device. So for example, Android TV device owners do not need to have the Google Assistant currently running on the Android TV device. Nor does an Android TV device need to be updated to Android 7.0 (Nougat) as it seems to work on non-Google Assistant Android TV units as well as ones running on Android 6.0 (Marshmallow). One of the caveats though is that you do have to be specific with the commands and very much so when it comes to device names. For example, if you have more than one NVIDIA SHIELD in the home and they are not named different then the Assistant will likely have trouble knowing which one you are referring to. Same will be the case if you do not tell it the exact name of the Chromecast – even if you only have one Chromecast in the home and connected to your account. Those in need of confirming what names are currently associated with a Chromecast or Android TV device, this can be checked easily by opening up the 'Home' app and looking under 'Devices'.