I want a tablet the size of A4 paper. Anyone listening?

I have an iPhone, motorola photon, Kindle Fire, iPad RD and MBP. I like reading on iPad however i feel the screen size still desires something. I always hoped that someone would make a screen that would detach from the computer and work independently. However, that screen needs to be as big as the computer. I think the ideal size would be A4 (12 inches diagonal) and it would double down as my laptop screen.

I wish I could be more clear. I am tired.