mouse > track pad > analog stick
I want someone to design a mouse for the couch. Mouse provides superior aiming for any shooter games. Mouse isn't critical for movement however, I can move just fine with an analog stick. I'm not sure a trackpad would make movement any easier. First problem: wires. Solution: wireless. Easy. Second and largest problem: you need a surface. If you're on the couch you don't have a mouse surface. You could use your pants…
Already exists: Bluetooth mouse + lapdesk.
> Third problem: non-mouse hand. It needs a controller for movement. It can't be a keyboard, nobody is going to want a keyboard on their couch.
I use a lapdesk + laptop + mouse on my couch all the time (yeah, I could ditch the lapdesk and mouse, but a mouse is so much better than a trackpad, etc., that its worth it), so I don't see the problem with a small (e.g., netbook sized) keyboard + mouse as a couch controller combo, with a lapdesk -- for a dedicated gaming controller, design the a dedicated surface with the bluetooth connection and directly attach the mini keyboard and mouse to it and you're done.