A newly published European patent application (filed in summer 2012) reveals that Sony has put some amount of effort into developing a tablet-like controller interface, dubbed the EyePad (via Engadget). The existence of a patent, discovered by GameChup, doesn't necessarily mean that this is a thing that will happen and be sold. It's certainly noteworthy, especially with Sony's next-gen console reveal believed to be happening next week.
The name 'EyePad' is an evolution of Sony's motion-sensing EyeToy camera, though there's obviously a tricky tie to Apple's own wildly popular line of tablets. The patent doc describes an input device with six-axis motion sensors, joystick controls (only one analog stick is pictured in the design sketch), and lit edges that "provide a similar functionality to that of the illuminated ball of the Playstation Move." The would-be device is also equipped with a pair of cameras that, together, can sense depth in a manner similar to Microsoft's Kinect.
It's all very intriguing, though it's important to remain realistic about what we're seeing here. Patents are filed all the time, for all sorts of crazy ideas. The PS Vita makes it clear that Sony sees the value in touch-based controls, but this EyeToy could easily just be an experiment and nothing more.