I like the idea, but I don't think they can. During an at-bat, they can't show anything that might distract the batter. Plus they're not allowed to show replays of certain types of plays, including called third strikes, so that might be an issue as well if they show the pitch-tracker on the screen.
They update the balls and strikes in real time so I can't see why they wouldn't be allowed to show MPH and pitch type. Pitch placement I think would not be allowed by the umps.
