Sony has now made available its PlayStation Video app for Android TV via the Google Play Store. This is an app that is free to download on compatible devices. Speaking of which, while this seems to be a generic Android TV app, its compatibility is a little limited at the moment. For instance, the Play Store listing is currently showing compatibility for the NVIDIA SHIELD (both 2015 and 2017), but not the likes of the Xiaomi Mi Box, the Nexus Player, or LeEco's range of TV sets powered by Android TV. So at the moment it does seem as though you will need to own either a Sony TV set powered by Android TV, or the NVIDIA SHIELD, to make use of the app.
As for the actual purpose of the app, this is somewhat of a basic offering. In the shortest of terms, this is simply a video player which can be used to consume video content associated with the owner's PlayStation account, and specifically content purchased from the PlayStation Store. For those who do not already own any videos purchased through PlayStation, then this app might still be of use, as it does offer the option to directly buy and rent titles from within the app. Although this is only one of many places where video content can be accessed in this way.
If you are more interested in watching live TV content via PlayStation, then Sony's PlayStation Vue app is likely to be a much more suitable option. In contrast, Sony's PlayStation Vue app saw its Android TV support going live during the closing days of October, 2016. However, that route does require the user to pay a monthly subscription fee in return for unlimited access to TV content. So for those who are less interested in paying on a monthly basis for a dedicated subscription, then this PlayStation Video app might be a good alternative. As it does offer the option to rent the latest TV shows on a per-episode basis. Likewise, it is a cross-platform app, so whether content is purchased on an Android TV device, a PS3, or a PS4, the content will be accessible from any of those devices.