I currently have a simple shoutbox extension coded up currently for my own use but I am planning on making it more advanced with permissions etc for the public. It will be released in this thread.
Basically same settings as mchat with a few extra things such as being able to have this at the top of a forum of your choice. Say you have a general discussion forum on your board. You can place the chat in that forum.
I will release more features as I code them.