So like 5 years ago i had some pioneer nav unit (it was a piece of shit) but there were all these people hacking and modding the software to do all sorts of awesome things.  like adding buttons that weren't normally there, making physical buttons do extra stuff, just completely modding the UI.  

Are there people doing that at all on the NEX units?  I want to be able to push a button and have my backup cam come on.  My NEX4000 will not allow this.  

That unit was hackable. These units are not.

It would be cool, since we have the firmware, for someone to hack the code and play. Wish i had the expertise to Root or Jailbreak a NEX.

It would certainly be cool as it was with the first gen F series. I was a part of this effort it it was certainly exciting. Unfortunatly until someone with the know how does the same with the current units its not possible.

If you hold down your map button your rear camera will pop on. #readthereleasenotes

I could be wrong, but I believe the 4000 does not have Maps.  That said, you may want to try and press and hold the other buttons to get camera displayed.

sshams95 is correct, the nex4000 doesnt allow this.  I did read the release notes, and got all excited that i could maybe do this, but it doesnt work.  where other units have the MAP button, 4000's have a MUTE button, which doesnt bring up a camera no matter how you press/hold it.  Not sure why Pioneer would hold out on these units only.... theyre just being dicks i guess.  ha.  

You guys might like this article.  Not a user ready hack, but its being looked at.

https://fail0verflow.com/blog/2014/enhancing-the-avic-5000nex.html