The application might be made simpler and more user-friendly if at startup the lens could just be set to the hyperfocal distance
http://en.wikipedia.org/wiki/Hyperfocal_distance
and then just put up a message to "Adjust focus with soft-press of camera button if needed"

The hyperfocal distance may be acceptable for something as close as personal a web camera, unless someone gets closer than 3 or 4 feet (depends on what the hyperfocal distance turns out to be).