Interesting, both "extrawebcam", and the previously mentioned "sparkosoft" list being able to operate with most EOS models, but not the t4i.
It also doesn't seem to work with DAVID yet (t4i/650d has an "M" [manual] mode same as 550d and 600 (t2i, t3i), so I wonder if the problem is with an unreleased canon driver).
The t4i connects, and is recognized by the computer (it is capable of live view, and of being controlled by the computer), it is even recognized within DAVID in the drop down menu in the "hardware" section the same as the t2i / 550d is... but it doesn't show the image when live view is selected, and if you just choose "calibrate", a warning window pops up (the same message as Waltermo saw with another camera [the c920 possibly?], it says "the image is too bright", or a similar message (I will check exactly what it says soon).
But it seems like it might be possible to get the t4i running one day ( in terms of reasons why it would be nice to see it work with david, the sensor is slightly better, more settings, higher iso range, faster aperture, and provides a nicer option for "secondary usage" in addition to working with the amazing DAVID).