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