I have just purchased the PDmovie remote live air. It's incredibly light, easy to use, and is free from any cable. The automatic calibration does not always work, but the manual calibration is very easy to make. For a one man shooting style, that's the best thing I have ever used as a follow focus, and even cheaper than most mechanical ones. I use it with an iscorama 36, which can be a pain in the -bip- to focus, and it has completely solved the problem.
https://www.youtube.com/watch?v=rxmKcXbjz-M