You mean like here

https://i.ytimg.com/vi/mbTqcqOLqWI/0.jpg
or here
http://symbianworld.org/wp-content/u...axy-S-wave.jpg

That's LAUGHABLY BAD compared to a mirror. Your rear view has to be able to be taken in completely in a 1/4 second glance, not "well, if I look at it for a few seconds I can pretty much tell what's going on."

There's a reason that eInk still is selling very well. It's because LCDs are miserable to read from outside, whereas eInk gets better the brighter the environment.

Also remember, with a mirror, reflections are the object of the thing. Reflections off the front glass are not an issue, they're at worst a slight ghost of the image you're looking for. With a phone, the reflection can be very damaging to understanding what's on the screen if the reflection is very busy.

With a mirror, the brighter the light, the BETTER it gets.

You'll notice that when they have a rear view monitor in a car, it's inside and underneath a big sun shield.