The thing is, there aren't many cheap flat video panels available for replacement that I've seen. A 5-inch CRT-based TV (which I've seen for as little as $25!) would protrude way too far out of the wall (typical depth comes close to 10" for these TV's). Are there any low-end B/W LCD panels that take NTSC input out there? I'd be happy to find them either in home-intercom type panels already or as a raw subassembly with power and NTSC jacks.
I know that the automotive electronics places have 7" or 9" color NTSC-in color LCD panels in the ~$150 range, but they seem a little excessive for this application.