Awesome stuff. My Hobbit is suppose to be shipping today and this was one of the things I was eager to play with (besides playing an awesome game).
I had, a very basic, live stream of my Joker Poker to the web at one point. I was using Pascal's all in one board for the system, and it had a i2c port for a large display. I was able to use an Arduino to monitor those lines and then update an html page with an image of the back glass with the current score in a matching font. (with poorly written html code)
Thats as far as I got.
But pinball on a full linux machine is going to be fun to play with.
Keep it up!