and I don't mean by any primitive way of control from the PC,
I mean a more sophisticated one,does that make sense? is it possible?
I don't see any drama doing that, you'll have to come up with a protocol and implement some hysterisis in the control loop.
and i was assuming i will need an additional psu..
You will need something external to the Arduino to power the servo, however if you're running the Arduino from 12v then use the same PSU for the servo.
Rob