Perhaps if this was stated clearly in your 1st post, us naysayers see your intent as opposed to presuming the inevitable; watching while driving.
At one time when cellphones and navigation were introduced, crashes from distracted driving occurred which led to laws against it. Meanwhile, I saw local police driving in patrol vehicles with cellphone stuck to one ear......... Hypocrisy in America. During this time, factory navigation was programmed to disable button/touchscreen operation while driving. Work arounds were discussed and used. Videos from aftermarket manufacturers already allowed this for watching video CDs or gaming. Fast forward to hands free phones bluetoothed to infotainment systems along with navigation on the go with tweaks to allow voice recognition and steering wheel buttons to maintain hands on driving instead of holding a phone for texting, calls, navigation. Improvements in driving safely while using distracting devices. And clips, suction cup mounts to hold phones near eye level, on the dash or under the rear view mirror for heads up driving.
I'm sure there's a way to couple external devices like your idea to watch live or recorded video. Where there's a will, there's a way.