Compact, portable screens seem like a no-brainer to me. My MBA display is less than half an inch thick. Why does my desktop screen need to be significantly thicker? Why not use the same panels from laptops to build a display that can be used both on the desktop and for portable use? I love to use one large/two smaller screens when coding - and I want a display that I can pack into my bag along with my main display and use at a coffee shop. The panels themselves are generally cheap (it's something of a commodity market, but depending on the display size/specs they run $35 to $90)
When I originally started researching this, there were two problems, both of which have been (pretty much) solved:
1 - Connectivity. Laptop panels generally use LVDS, which from my understanding are bit-reversed versions of DVI, possibly with some extra baggage. So you needed to have some intermediary processing, which was then (and is still) possible using a DisplayLink chip. The DisplayLink chip basically uses CPU power to create a virtual DVI/LVDS port over USB. The advantage of DisplayLink is that it negates the necessity for even using the Thunderbolt/DVI/Displayport output of your laptop, and allows you to simply plug in via USB and go. But the chips cost ~$15 each, require non-trivial integration, and use up CPU. As Andrzej mentions, displays are moving towards eDisplayPort, which means you can pretty much plug them in directly.
2 - Power draw. For the display to work well as a portable device, it should be possible to power it via USB alone. USB 2.0 standard is 5V and 0.5A, so 2.5W, which isn't sufficient. But USB 3.0 is 0.9A, bring the total up to 4.5W. As Andrzej mentions, the iPad display can be powered off the Displayport power (3.3W, 0.5A, ~1.9W), and with a step-up convertor you should just about be able to power the backlight up to max brightness from the USB port.
Both those problems are now fixed. You can now build an external display, either using an iPad panel, or that from a 13" MBA or (possibly that of a MBP Retina, not sure about the power requirements there). Then you have an extremely slim, awesome external display that's completely portable and powered by USB.
Some companies have been building crappy versions of this using DisplayLink chips, but I really want to see something with a clean, minimal design and way higher resolution. I'd try at it myself, but I'm busy trying to build software to enable better online political activism. If anyone out there is interested, I'd love to help, either with funding or advice.
A few examples of products that do this (not very well) using DisplayLink chips:
- http://www.amazon.com/Lenovo-ThinkVision-LT1421-Widescreen-M...
- http://www.amazon.com/AOC-E1649FWU-USB-Powered-Portable-Moni...
- http://www.amazon.com/Toshiba-14-inch-Ultra-portable-Mobile-...