I'm pretty sure all of the Canon EF autofocus lenses can do "AF Servo" where they can follow a moving subject. This is a function of the camera, not the lens AFAIK
. Some lenses are more responsive than others - my 70-200 "L" lens has an ultrasonic ring motor, which makes it faster to focus than some of the lower-end lenses.
There are also new "STM" stepper-motor lenses, which are optimized for continuous focus during video shooting (which the t4i supports as well), but this still works with regular lenses, they're just louder and potentially slower, but it still works.