In my experience I have found Monopods very useful in steadying the camera/lens combination. Whilst they do not offer the stability of a tripod, I have found that they reduce the amplitude of camera/lens movement and help keep any movement restricted to a much smaller range.
I have also found them very useful in supporting the weight of camera/lens, reducing the fatigue from just holding the equipment.
I reckon that it could be a useful accessory and I suspect it would not only dampen any movement but it would also transfer the weight of camera/lens to the hips thus reducing strain on the arm.
It would also keep you more mobile if you had to move quickly, no need to lift the extended monopod from the ground and risk fouling it as you move, or catching it in foliage.