As I envision it, the controller device would have two components or devices connected wirelessly or via a wired similar to the Wii nunchaku controller:
Device 1 (default "right hand")
- Identical to a mouse in use and function except without the need for a consistent flat surface.
- Should be usable by lying your hand on your lap or on the chair/couch at your side (any position as long as it's comfortable and you can move your hand).
- Movement could be detected by an internal sensor or another mechanism such as an external sensor bar.
- Precision shouldn't be affected by the default placement of the device in any way.
- The device could be shaped to emulate a mouse or adopt a completely new design such as a sphere or malleable object such as a isometric strength "squeeze" ball.
- The device should support a small number of buttons similar to a gaming mouse.
- The device should be ambidextrous.
Device 2 (default "left hand")
- Includes an analog stick, d-pad and trigger buttons.
- Is held in the hand and can be placed anywhere, position and orientation are irrelevant.
- The device should be ambidextrous.
This type of nunchaku-style controller would provide superior ergonomics and emulate the mouse and keyboard experience almost identically except with the inclusion of an analog stick and d-pad for directional input and without the easy text input and large number of keys that a keyboard provides. The key technical challenge is building a mouse-style device that isn't dependent upon placement or surface area. Some type of 3D positional tracking "flattened" to a 2D plane might accomplish this. Think: a specialized Wii/Kinect sensor reworked to sense more precise movement at a much smaller scale instead of large body-size movements. Placing your hand in your lap or on the couch in a resting position should be no different from placing it on a mousepad.
I have a hard time believing this isn't possible with our current technology and would be far superior to a touchpad controller, IMHO.