Even after reading through this thread again, I'm still not sure whether we're talking about a reversing camera or a rear facing recording camera but I've 2 types of the former and one of the latter!
For reversing camera, there's a conventional (ie. comes on when you engage reverse) hard wired Kenwood displaying on the screen of my Kenwood Head Unit (with audible and visual signals) - all installed by Absolut 5 (along with the front Kenwood recorder). I've also got an Auto Vox TW1 fixed to my towbar mounted bike rack. The 'camera end' is totally wireless (as indicated by the 'TW' in the name) and it comes with a separate monitor which plugs into a 12V socket - to activate the camera, you simply press a switch on the monitor and the rear view (with distance bars) comes on for a pre-determined length of time. Before I got the Kenwood mentioned above, I actually had two of the Auto Vox cameras, one on the van rear number plate and one on the bike rack and it was easy to switch between them but that's obviously now unnecessary as I only need one fitted to the bike rack. It's a great bit of kit with a clear picture which has never shown any electro magnetic compatibility issue and the only real downsides are the need for an extra screen, the camera has to be recharged and it's a bit fugly. That said, none are real issues for me as my cockpit layout using a 'seatshelf' with the double bech means that the monitor is quite discrete and a charge lasts a very long time - I've had the loaded rack on the van for 6 weeks on a European road trip and according the the monitor the battery still had plenty of life in it when we got home in any even, it's easy to charge). As to its looks, I can put up with it!
For a recording rear facing camera, I use a comparatively cheap Orskey which is another great bit of kit. At 1080p, It's video quality is very good (IMHO better than the Kenwood in the front!). I've got it suckered to the rear window on my tailgate and it's powered via 12V into a mini USB socket and the cable is almost all out of sight running from the camera, over the top of the wardrobe, behind the furniture and under the front mat into an ignition switched piggy back fuse.