Can any model iPhone be used as a backup camera MONITOR for a car?

There are many vehicle backup cameras on the market but I would like to know if the iPhone can be used as a backup camera monitor. Just brainstorming some ideas. Can an external camera be hooked up to the iPhone and the video be displayed on the screen similar to the live view you get when using the camera to take a picture. Or is there an app that makes this possible? Or any other ideas some of you may have come across? I'll go though the reasons for why I want to do this so i don't get responses like "why don't you just buy a backup camera". Or "Way don't you get bigger mirrors" I really just want the iPhone to do this and maybe it's just not possible;-(
1. I have an iphone mount on my motorcycle just below the gauge cluster.
2. I have power going the phone from the bike charging it so power usage is no issue.
3. I have bucktooth speakers mounted in my helmet and can listen to music and make phone calls.
i can also talk other riders, riding with me.
4. I have access to goole maps and turn by turn directions on the iPhone for current location and able to look for new roads to ride on.
5. I understand the safety issues and I keep my attention on the road.
So I would like to also use the iphone as a backup camera monitor or more importantly as a rear view mirror. I do have 2 rear view mirrors on my bike but the view right behind me is blocked by my shoulders and I would like to know what is going on right behind me. Mirror extensions are not enough to solve the problem and cause more stress on the upper faring. I have looked this up on the web and found the exact title from others looking to do the same thing but the responses had nothing to do with the original question??? Not even close. So maybe this is not possible or maybe it would be a good project for someone. I'm not to concerned with expense cause i'm into the convenience of having everything on one device. So thanks in advance for your responses....