Recently, NVIDIA’s SHIELD became the first Android TV device to get access to OK Google and the Google Assistant. The thing is, you really need the TV to be on in order to really make the most of it---but a new setting will still let you use it even when the screen is off.
Before we get into how to do that, though, let's first talk about what to expect when using this feature. First, the functionality is going to be pretty limited when your TV is off. If you're using it to, say, turn your lights on or off (or comparable smarthome features that don't require audible or visual feedback), that should work perfectly.
But since neither the SHIELD nor the controller have speakers on them, it won't be able to answer questions---like "what's the weather going to be tomorrow." The exception here is if you have a soundbar or separate receiver and speakers attached to your TV. Simply leave the soundbar on to hear the Assistant. Of course, that may not work with every TV and every soundbar, either---you're just going to have to experiment with it.
NVIDIA is likely working on some alternative solutions to these quandaries, but until they figure something out, this is what you get. Despite its shortcomings, however, it's definitely still worth using---especially if you don't have something like Google Home to do the job.
NOTE: Always listening is only supported on the 2017 remodeled controller, which is fully compatible with the first generation SHIELD set-top box.
Alright! With that out of the way, jump into SHIELD's settings menu: scroll all the way to the bottom row and click on the gear icon.
From there, head down to the System entry and give it a click.
There are a few options here, but you're looking for the last one: Enable "OK Google" when TV is off." You'll also note this in in beta, so don't be surprised if its slightly buggy at times.
When you click into this menu, a caveat will be displayed letting you know that you'll need to at least leave your soundbar on in order to hear the Assistant, which we already mentioned above.
Go ahead and toggle that bad boy on, and away you go. Good stuff.
From that point forward, you should be able to better integrate SHIELD into your smart home setup, treating it as an additional Google Home product---especially if integrated with Samsung's SmartThings link. Very cool stuff.