I had the same thought last week when I saw a write up about the new GBA.
I think it would make an excellent "satellite" display for a trunk/under seat mounted empeg.

Not sure on the interface on the new GBA though, from previous versions it uses some sort of weird not-serial interface, which a small micro could no doubt talk to.

BTW: How bright is the screen in the new GBA in sunlight? Seemed to me to be the major drawback with the original GBA, but I would expect that to be removed this time round.
[hopefully].