We've seen like a hundred (not really but it seems like it) 4K TVs at CES so far, but apparently there are UltraHD tablets too. Panasonic just whipped out one of these pixel-packed devices at its keynote. And it's enormous.
The screen looks beautiful because, duh, double pixels. It looks super thin, runs Windows 8 and it comes with a stylus. But it has a 20-inch screen. You can't carry that comfortably. If it ever comes out, it'll be strictly for professional applications and ludicrously expensive.