I'm one of the founders of Visionect (http://www.visionect.com), that focuses on EPD solutions. We offer a bunch of development kits (6"-32") that can be easily productivized (our customers are building bus stops, traffic signs, museum signage, room booking systems,...)

There are no technological limitations in terms of the panel size (backplane technology is practically the same as TFT), but its rather a volume question.

We see this "personal display" theme pop-up quite often on our email, but the pricing is prohibitive (even compared to high quality and high resolution LCD consumer panel) and the refresh rate does impose a lot of limitations on what you can do.

I think that E Ink is best used for displaying information and use cases that benefit from E Ink itself (think high contrast, outdoor scenarios, indoor units that work 24/7, applications where you can power a display with a battery and reduce installation complexity).