In my app I am giving the option for users to share information with other users of my app. After two users decide to share, every time one of the sharers updates the app I need an alert/notification sent to the phone of the other user so that the app updates automatically with the new information. So basically I am looking for something along the lines of hidden text messages, which when received the app will automatically update.
Can anyone point me in the direction of what to use? What Android has to offer to accomplish this?