It's totally pointless except for the mentioned front grill cam. As long as you're doing it with the stock head unit and no mods you cannot watch video UNLESS the car is in Park and the Parking Break is set.
Also the HU resolution sucks compared anything like an iPad or tablet anyways...
Plug an rca AV cable with 4 pole 3.5m connector into the aux port. (Commonly used as a camcorder input cable) You now have input to the head unit to play video.
