I rarely get to mess with the hardware end anymore so I am jumping the gun a little by making this post now.
Regardless I recently purchased a interact mobile monitor 5.4 inch lcd and I'm about to put it in my cabinet as a secondary Monitor. To my knowledge this will be the first dual monitor mame cabinet that actually makes use of the second screen (there is an xbox cab out there that simply displays the same picture on both monitors but imho that isn't particularly useful).
The screen is rca input only, but upon cracking it open i'm confident that I can hack in vga or at the least svideo input.
Now the question is, what do I do with it? Well dk sorta supports dual screen, but i'll be writing a custom app that'll run independant of the fe and anything else for that matter and get data from any app that cares to broadcast to it.
Also I am in the process of tweaking/hacking various emus that can take advantage of the new real-estate. I have already successfully re-written my visual pinmame wrapper to automatically maxamize the pinmame dmd display on the secondary monitor, making it nice and big. This way the table is on one screen and the scoreboard is on another, as it's supposed to be.

Chankast supports emulation of the little memory unit lcd displays now. I think it would be good to position those up on the secondary display as well. It should be virtually the same hack, in principal. My biggest challenge will be making a patch for mame that takes the dual screen games (playchoice, ect) and actually spans them over two real displays, thus the games are displayed as they are intended.
Of course there will be a great deal of hacking on the hardware end too. Mostly converting the signal and making a custom housing and adjustable mounting bracket for it.
I am documenting the process and will have a webpage up in a month or so for anyone who is interested.
I hope everyone is as excited about this as I am because by the time I am done, putting a second display on a mame cab will actually be practical as we will all have some actual software to run on it.

I've already gotten the monitor to work as a secondary display using the tv-out of a second video card I had lying around. Until I make further progress, enjoy this fuzzy pic of the monitor displaying wmp.

