auto focus for manual lenses would be possible with some auto focus code and an attachable servo
laser triangulation, ir or ultrasonic distance measurement combined with a servo or microstepper attached to a follow focus (example http://www.philipbloom.net/wp-content/uploads/2009/06/microff_v2_15mm_lg1.jpg ) to adjust the lens focus according to distance. different lenses might need different adjustments.
i have used a Sony EX3 with Fujinon zoom optics which has autofocus and electric zoom. to that was 2 controllers attached, left and right on the handles of a sachtler tripod.
this for focus: Fujinon EPD-1CA
and this for zoom: Fujinon ERD-T22 Zoom
for a broadcast studio setup this is really great!
there are a lot of focus systems for manual zoom optics. there is one part with a servo attached to the lens and one controller, attached with a cable or wireless. i think a cable is better for less delay.
most of them are quit expensive, but there are DIY projects out there.
if we have such a system, the axiom firmware can control it for automatic focussing or manual focus with a smartphone.
we could just attach a servo with a housing to our rig since we have a board to control it. maybe 2 for focus and zoom.
This can be grouped in with the Open Source Arduino Follow Focus, motor controlled auto focus using various methods, one of which included a manual calibration method of calibrating a manual focus lens or unknown lens.