Well, my car’s a 2010 model, with the Connect Premium/satnav system. If you have an earlier model, or one without Connect Premium, you'll need a slightly different setup. The solution shown here works for 2010 models onwards.
I believe that currently the 2013 GT Edition (the most expensive of the 3 options, at £37k+) includes a reversing camera as standard, but no other models have it.
I got a new reversing camera off Ebay for £21.50 ( HERE ) and a wiring loom made by Paul_S (electronics genius and Admin Bloke on this site) for £60 delivered ( HERE ), making a total of £81.50 – Bargain!
I installed it myself (took about half a day, at my snail’s pace). It wasn’t hard to do. No cutting or drilling (the camera simply replaces one of the number plate lights and it has a replacement light included in the unit). The camera image is so good that I just want to drive everywhere backwards – I dare say this urge will wear off eventually.
Result – one delighted customer!
I would thoroughly recommend this mod. The rear view on 370z's is almost non-existent, so you need at least a camera (I’m thinking that maybe I need reversing sensors too).
If you have any questions, please ask.