We’re not sure exactly when this feature launched, but it appears that you can now use your voice through Google Now to send a Hangouts Message. All you need to say is, “Send a Hangouts message” or “Send a chat message”. You can also add a name to streamline it as in “Send a Hangouts message to Jodie” or even add the message is in “Send a Hangouts message to Jodie What do you want for dinner?”.
For those of you that use Hangouts for your SMS messages as well, unfortunately this voice command will not work for SMS messages. This command will always look for a gmail address for the person of your choosing. You can still send SMS messages through Google Now by saying “Sending a message to _______”, but it will go through the default SMS app on your phone.
Another thing to point out is that this new found functionality does not work with Android Wear. If you say “Send a Hangouts message” into the microphone of your Android Wear smartwatch, you will be given a prompt to open the app on your phone. Hopefully Google will rectify it soon because that functionality is desperately needed.