Autofocus with DSLR and Lens

Here is one setup similar to the one Chris describes that I have been thinking of making:
http://www.cloudynights.com/topic/523647-slr-lens-qsi-setup-first-light/
A timing belt, stepper motor, a pulley, existing robofocus controller and some way of holding all these together so that focusing is repeatable - a project for the winter

I have seen another setup on CN, but can't seem to find it now. Another article I chanced upon refers to the "WalterLee Heliofocus":
http://www.astrofocustechnology.com/heliFocusDeluxe.htm

Ajay