Follow Focus for DSLRs

Everyone's talking about the new Canon HD DSLRs, so I'll jump on the bandwagon...
Mark Wilson at Gizmodo has put up a couple of posts about DIY focus rigs for DSLR cameras. This one's ugly, but looks somewhat functional. This one's pretty, simple, and cheap, but probably not very useful as a follow focus. I like this one, posted by a commenter. It seems to be a nice combination of simplicity and usefulness:

"I'm not an experienced cinematographer. But I want to use the Canon 5D Mark II to shoot decent quality video—without expensive rails, follow-focus rigs, matte-boxes, etc.

The solution, for me, needed to be portable/ultralight, SIMPLE, and as cheap as possible. Most often, I’m rack-focusing between preset points. The sample movie shows the rig in action. Remember, I am new at this, so you can probably rack more smoothly and might use a better tripod. The rig itself is very smooth and does not create much vibration. With two people, it should be okay for follow-focus.

Just for fun, I’m calling this “The Scocus Ring”-- for Scott focus ring--but call it what you want! It is essentially an off-the-shelf MegaClamp with foam buffers to protect the lens, a simple picture hook “needle” indicator, and a bag of rubber bands."