Always-listening voice assistants, like Google Now/Assistant or Alexa, can't really tell the difference between you talking and someone else (unless you have Trusted Voice enabled on Android). Maybe you've watched a few tech videos where someone said "Ok Google," and your phone started talking back. Read More
Google started rolling out a massive improvement to voice search in the Google Search app last week by enabling "Ok Google" hotword detection everywhere. Really cool, but it has been slowly making its way to users on a per-account basis. Tired of waiting? Just a few taps, and you can (maybe) get instant access to the feature. Note: Probably US English only.