I got a box full of farkles from Murph yesterday and one of them was the Throttle Rocker. I gave it a try on my way into work this morning and let me tell you, I should have got one of these a LONG time ago! It installs in seconds and works great. I can totally relax my hand now and still control the throttle easy as can be. The TR works great even in heavy traffic. For under $11 you can't go wrong.
Many years ago I bought a rubber, strap-around bump thing that does sorta the same thing. I never really liked it, since it would interfere with "holding on" and quick braking (with no throttle). But, I am willing to give this design a try, so it is on my to-order list now.