I looked this up a while ago and managed to disable the annoying beep that comes on when the rear-view camera is active and the prius is in reverse.. but recently my battery died and reset all my settings.. looking it up was a pain, so I wanted to post how to do it:
1. While stepping on the brake pedal, press the start button to turn the car on.
2. Press the trip/odometer button until "ODO" appears on the dashboard (if it's already in that mode when you start the car, press the button three times to cycle through the "Trip" modes until you're back to "ODO" mode).
3. Press the power button to turn the car off.
4. While stepping on the brake pedal, press the start button to restart the car.
5. Press and hold the trip/odometer button within five seconds of starting the car and keep pressing it for at least 15 seconds, and keep it pressed down.
6. While still holding the trip/odometer button from the step before, but after 15 seconds have elapsed, shift the car into reverse and quickly press the park button. Now release the button.
7. Note that the trip/odometer display will show "b on" instead of miles.
8. Press the trip/odometer button until the display shows "b off."
9. Press the Power button to turn the car off.
10. When you start the Prius back up, the reverse beep will be gone.
11. (Optional) Serve yourself a healthy pour of your favorite scotch whiskey, you've earned it.
... Now to take it a step further, try to get your camera to be visible at ANY time, not just when you're backing up! Linky: http://www.evnut.com/prius_mfd_video.htm