This little gizmo came with a used ETX 90 that I bought, but it didn't fit the focus shaft. I e-mailed the seller who said that he bought it but never tried installing it. I suspect it would probably fit an ETX 60 or 70 though.
To use it, you unscrew your focus knob from the ETX, place it on the end of the "focus" cable and tighten down the small allen screws. The other end of the cable tightens down on the focuser shaft of the ETX. It works pretty well--I ended up buying another one for my ETX.
You can have this one for $5 shipped--ConUS only. Paypal (+3%), cash or mo okay.