I fitted a front and rear camera probably cost me a total of $50 I got the two cameras off eBay and connected them up to my head unit, you can buy wireless ones that are pretty simple to install and are about $140 I think my mate paid. Hope this helps.
Oh I have a d22 I just have an aftermarket screen, but I think you can get the wireless unit with a mirror display as well, have a captain cook on eBay or autobarn sell them too.
Hi i am in the progress of installing a unit to my 2010 st i got the unit from Elinz electrical with 7" screen which i am working on installing above the stereo where that cover tray is. have just got fixed in place now and will continue to work on a way for it to fold down.
I have put a picture of current mounting position in my garage. the 7" screen fits perfectly with the screw that holds the dash panel in lining up perfectly with a hole in the monitor's frame.