Like many of you I have also thought about how to produce "modern" video
output from an Apple II. My personal opinion as to what would work the
best would be a second-sight style card using more modern components.
For example, there are fairly powerful ARM SoC's with integrated
graphics available that would be more than fast enough to fully emulate
all Apple II graphics modes.
In fact, I'd love to make such a thing myself. Unfortunately I'm not up
to it on the hardware side. The software isn't a big deal. My NTSC video
modification for Applewin (http://wsxyz.net/applewin.html) is 90% of the
way there already, as it works by simply pulling bytes out of video
memory and running them bit-by-bit through some fairly simple code that
imperfectly (but sufficiently) duplicates NTSC signal processing. All
that would be necessary (in a hand-wavy sort of way) is to run this code
on a card that captures the video bytes from the bus and displays them
just as it does in the emulator.
I was even considering trying out a BeagleBone
(http://beagleboard.org/bone/) to see if I could use the 40-or-so GPIOs
available on the board to interface with the Apple bus to do the job.
However in that case the ARM SoC would basically have to sample the bus
at a high enough rate and I'm not sure it would be up to the task, even
though it's a 720 MHz core. Also, it would be kind of ugly having a
beagle bone flopping around in or behind the Apple instead of a nice
clean card, but it might be worth trying out anyway.
Any thoughts?