The Focusmate Camera Focusing Platform gives you the ability to control the focus / zoom of your manual-focus DSLR remotely. It is machined from solid CNC aluminum and the knobs have rounded heads, preventing excessive marring of your dovetail plates.
If you own a Robofocus, this platform is already compatible and is easy to bolt on. The motor attaches to your camera's lens with a notched drive belt. Tension can be adjusted by simply moving the slider back and forth.