I don't think this necesseraly is what you are looking for, but it is an example of how to use jit.rota for zooming.
Remember to change the message argument for the "anchor_x $1" objects if you change the screen resolution from 1440x900.
Check out the help file for jit.rota
Regarding video camera check out jitter tutorial 21-23.
However, when I tried it, it was as simple as connecting a firewire -> dv cable to my mac and press the message open and send it to a jit.qt.grab connected to a jit.window/jit.pwindow.
Good luck. It's easy!
PS: Check out baz tutorials on youtube. He does something with jit.rota search something like "video zoom amplitude"...