Ever since the Google Assistant first launched on the 2016 Pixel and Home, there have been some differences between the AI on both platforms. Google Assistant can do certain things on Google Home that it can't on phones and vice versa. Google's been working hard at bridging that gap, and in the latest attempt to do this, users are now gaining the option to prompt the Assistant on their phone by saying "Hey, Google."
You've been able to use this command on Google Home since its release, but the only way to get the Assistant's attention on mobile has been the classic "Ok, Google" phrase. There's nothing wrong with "Ok, Google", but "Hey, Google" is a lot more natural and just rolls off the tongue better than the other option. As someone who uses "Hey, Google" about 99% of the time with my Google Home rather than "Ok, Google", this is awesome news.
However, in that same breath, it's also got some people concerned.
A lot of users (myself included) have taken to using "Ok, Google" for their phone and "Hey, Google" for Google Home as to not trigger both devices at the same time. With "Hey, Google" now coming to Assistant on phones, it's much more likely that you'll turn on the Assistant on your phone and Google Home when just trying to get the attention of one of them.
If this sounds like a nightmare, fret not. You'll get a notification when the update reaches you saying that you can now train the Google Assitant to respond with the "Hey, Google" command, but you aren't required to do so if you don't want to. Use it if you want, or ignore it if you don't.
I've already gotten the option to use the "Hey, Google" command on my Pixel 2 XL, so keep an eye out for it on your device if you haven't seen it yet.