I have a Google Voice number, and can send and receive SMS messages using both the website (through gmail.com) or from the Hangouts app on my Galaxy S3.
If I have an open desktop web browser on Gmail, and receive an SMS message, my browser pops up the message and gives me a notification, but nothing happens on my phone (I can open Hangouts and see the message - I just don't get any notification). This happens even if my web browser doesn't even have the Gmail tab active, just if it's open in the background.
If my web browser is closed, then the notification happens on my phone.
I'm assuming Hangouts thinks that since the message came through on my browser, that I don't need to be notified on the phone.
I don't see any setting on Gmail, Google Voice website, or in the Android app for disabling this - anyone have any ideas on how I can get notifications on my phone even if I have a browser open?