If you're looking to do some remote focus pulling, the wireless systems can be a bit 'finicky'. A Wired electronic remote follow focus system works with a long cable so the camera operator can move about, and the puller can control focus with a remote video screen. This particular one (above) uses a basic '3.5mm stereo' cable for the remote tether. Looking back at some of the older videos, this new electronic follow focus has been a work in progress for at least several months. The final version finally has shown up on eBay with what looks like a similar beefy servo as in the Jag35 kit and starts at only $199 (seen here).
The video above has the Servo mounted on the stiff Zoom ring (not focus ring) to showcase it's strength. There are two different versions available. One with a A/B programmable focus points, and one is just a basic electronic follow focus. The speed of the movement can be adjusted on the remote as well. There's a few other videos showing the effectiveness of programmed A/B stops, and a closer look at the Remote (keep in mind that's the older version ff) on the eBay page (click here).
GT35Pro Electronic Wired Remote DSLR Follow Focus
There's nothing "stiff" about that zoom ring; in fact the zoom on that lens is one of the lightest of all of Canon's zooms. It's the 18-55mm kit lens. The demonstration shows nothing about that motor's strength.
Holy Poopers a 20D!!!!
This thing looks pretty killer, I got an odd diy rig that this would fit the bill for. I remember back in the diy lens adapter days on the hv20 these guys used to make rigs, not sure about how well they're known these days but I don't recall any horror stories about them... I can't justify buying the thing now, but I like it!
My concern with this guy would be that he's got 96% positive feedback, which is king of low, and he does not allow returns. On the video his device looks like it's working fine.