Currently I am developing an extension (script) that will play a noise similar to that of a ping when you get a new message. Doing this may be difficult, I don't know yet. Here I will post ideas and possible ways to do things.
- Find the rail ".Rail"
- Find the Private Message container ".PrivateChatList"
- Look to see if any elements have class unread ".User unread"
- If an element has that class, play ping sound.