What's stopping us from making something like http://www.yankodesign.com/2013/01/29/best-keyboard-ever/? Samsung came out with a phone in 2010 with an e-ink keyboard (Samsung Zeal). Are there any unsolved obstacles preventing this kind of keyboard from becoming a reality?

I would imagine such a keyboard, even at a $300 price point, would be massively more successful than the Optimus Maximus ever was.

To entice users even more, it could probably be made water resistant by not including any ports and using appropriate switches. It could come with a USB-powered inductive charging matt that you place the keyboard on top of to charge.