At the end of last month, Google announced that Duo would be coming to the slightly bigger screen in "the coming weeks." Sure enough, the video calling app is now available on Android TV — you can install it remotely from Google Play on the web or in the Play Store app on your device itself — but it's not fully functional just yet.
I managed to download Duo on my Shield TV and run in, but this isn't the full-featured experience you may expect. First of all, there's no launcher icon for Duo, so the only way to launch it is via the apps list in the Android TV settings. Once you've gone through the permissions so that your contact list appears, it is possible to make a call using the microphone on my remote, although only voice since I don't have a webcam attached to my Shield.
It doesn't yet seem possible to receive calls to the Duo app on Android TV, either. So it's clearly not quite ready for the prime time, despite the fact that you can install it and make calls. Google will surely fix this in a future update, so we'll have to keep an eye on it.
- Android TV Guide