I have released my Media Center Front Display Panel SDK. You can find API documentation here.
This is an SDK that I created to give you a managed API and State Aggregator to get notified of state from the Media Center State Aggregator Service. If you have a Windows Media Center 2004 machine you can implement IFrontPanelDisplay and do what you want with the information. In other words, if you want to write some code that gets notified of things like current tv show, elapsed time, volume level and so on then this is for you.
For example, Ian Kennedy (a fellow MSFT employee) wrote a C# implementation for the Hitachi HD44780 Parallel Port Vacuum Fluorescent Display that comes with our D.VINE Media Center cases. I wrote an implementation for my machine using his code and voilà. If you happen to have a Media Center box with such a VFD you can feel free to download it.