Dashboard communication?

I know this must exist somewhere but I can’t find it. I’m still looking.

What I am looking to do is make the dashboard in my WP install a communication center of some sort between the different writers on my site.

There is currently three writers and i want to be able to communicate with them via the dashboard in a “post” style system.

Any idea where I may find this? I already have WP Dash Note but its just not enough, I need something a bit more in depth. I’d also like it if they could post to this as well.