It seems Sony has been working on a variety of controllers for PS4.
This new patent which was filed in 2012, is about something called the ‘PlayStation Eyepad’.
It has the form factor of a tablet and can work in conjunction with cameras that are actually on both sides of the device to generate 3D virtual buttons and more. You can then use it as any other normal controller. It also features a touch-pad, which the PS4 controller was also rumored to have.
Source & Source
Here’s the official description for it:
 Referring now to Figure 2, an input device 1000, hereafter referred to as the EyePad, is typically a panel, tablet or slab-like device comprising one or more illuminated regions 1010, two stereoscopic video cameras 1030A(L,R) and 1030B(L,R), and optionally a touch sensitive surface 1020 (hereafter referred to as a touchpad).
An input device for an entertainment device comprises a first main surface, one or more side edges, one or more motion sensors operable to generate motion data, and a wireless communicator for transmitting the motion data to the entertainment device, wherein an elongate illuminated region extends along some or all of one or more of the side edges; in addition the input device may comprise a first stereoscopic camera and a second stereoscopic camera having respective viewpoints located at opposing corners of a first area of the main surface, the field of view of each stereoscopic camera encompassing a first volume of space immediately above the first area, wherein the first and second stereoscopic cameras are operable to generate respective stereoscopic images, from which a first depth map and complementary second depth map may be generated for opposite sides of an object placed within the first volume of space.