No idea how technically feasible that is, but "tiling" could be one way to build a really high-res 20"+ display without requiring absurdly large, continuous error-free panels.
1) Get just the panels off ebay for $60-$80 /each.
2) You can get the spec sheets for the panels with enough Googling. It's a 6-bit (yeah, not 8-bit) LVDS signal, same as most modern laptops.
3) The toughest part. Create a DVI-> high-speed LVDS converter. There might be something already available, though. A quick google only shows a Toshiba DSI -> LVDS converter capped at 1080p.
Ballparking the LVDS clock rate: 2048 * 1536 * 6 * 60 Hz = 1.1 GHz
Interesting idea, though.
Have laptops made the switch yet? (since they use displayport externally seems like it would be in their interest to use it internally as well) In that case the new MPB panel would perhaps be more suitable (and probably cheaper in the end - as well as better quality (I'm assuming/hoping it has 8 bits, but I don't know)).
And with displayport you could just hook it up to a decent gamer graphic card and be done. I'm not sure how feasible 2048x1536 is for a single-link DVI (at 60 Hz you would probably be in trouble), and graphic cards with 4 dual link DVI connectors isn't exactly mainstream so you would have to get (at least two) active displayport to DL DVI adapters, and they are not cheap either.
While you're talking about big high res panels, I'd be happy with an extra little low res panel; any of the Nintendo DS screens, for example. But being able to use these old little panels could prevent some of them ending up in landfill.
I guess the other problem is the weirdly sub-optimal nature of multiple monitors - despite years of people wanting to use multiple monitors it's still a bit kludgy.
Essentially a bit of software to add other devices (ipads, phones etc.) as virtual screens
i have the second. it works ok.