Add a couple of features
When you miss text calls a popup on your phone should appear, something like this: http://www.iphonefaq.org/images/archives/message-jump.jpg Otherwise, the phone app does not allow you to increase the amount of times the phone rings. I am using Temple Bell and it goes around 3-4 times only. Otherwise, it is great!
When you get a reply to chat there will be a counter so you can exit the app and still know what is going on.