This can be either “OK Google” or “Hey Google” or something similar ... Here are those commands: There’s a lot of commands in this list and it’s likely not all of them.

Google Now can be awakened by saying “OK Google” from the screen of any device. In some devices, the command is Hey Google. You might wonder if it is possible to change this command to ...

in addition to the old “Ok Google” voice command. The “Hey Google” hotword is now live, and you’ll probably have to reconfigure the voice settings of your phone to start using it.