Once you find a way for vent and wow to access each others data the rest will be easy
One of my guildies used to use an addon that had vent details as an overlay but unfortunately it used the games 3D environment to draw the details on the screen. This ability was removed several patches back because people were using the same ability to get the game to tell people where exactly to go when in a raid rather than tell them what is happening and let them think what to do about it.
So, I reiterate what I said above, if you know of any existing addon that currently works with 4.0 and displays live vent details as they happen I should be able to hook up an infopanel for you.