Currently the EyeX SDK provides the X, Y, Z position for both the left and right eyes, as well as normalized X, Y, Z values. I use the left eye as the head position and had to do filtering myself since the SDK doesn’t yet do eye position filtering for you. I don’t know if the 4C is any better at this than older models, as the 4C is my first Tobii device.
I didn’t see anything specific for head tracking in the SDK, so there’s no access to pitch, yaw, or roll. I don’t know if it’s planned or how accurate it might be. Would be cool if the Tobii people joined our discussion! 🙂