I was talking about using as a secondary monitor slapped to the front of my desktop computer case. But if you want to use it on your mame cab, then you need a dual monitor video card, or 2 video cards, and a frontend that can handle outputtting to 2 screens.
Or, you could use a separate application that this multi-monitor aware to display information to the second screen, and talk to the frontend through some interprocess "pipe"
-PMF