Do other "on-demand" voice-activated apps use this same technique?
I know that Google Now, Siri, Amazon Echo, and others respond to commands like "Ok Google [...]". Those devices must necessarily be listening if they're to catch those voice commands, right? Or is there a more clever solution for recognizing predetermined phrases?
Phones usually have fixed-function low-power hardware dedicated to listening ambiently for phrases like "Ok Google." So yes, it is technically always on, but no, it's not understanding what you're saying or uploading it to the cloud.
I know that Google Now, Siri, Amazon Echo, and others respond to commands like "Ok Google [...]". Those devices must necessarily be listening if they're to catch those voice commands, right? Or is there a more clever solution for recognizing predetermined phrases?