The basic idea is that you harness your upper body to drive the bike, in addition to your legs. I think this calls for 2 things:
- Recumbent sitting position, so your upper body is upright as it would be at a gym.
- 3 or 4 wheels so balance is no longer an issue. If you're going to be flailing all your limbs, I don't think balance is going to happen.
The handles are hooked into the drive train via a standard crank mechanism. For the rowing motion, I would think you'd want to gear the handles down, so the row motion is about half the speed of the pedaling motion, otherwise you'll look like a silent movie of a gandy dancer railroad car.
The main challenge is going to be the steering. Since you're not on 2 wheels, you can't have lean steering. Perhaps the handles could move side-to-side as well for steering - I'm not sure how well that would work - could you provide power from your hands and steer at the same time?