My wife actually read 'the Christmas list' this year and got me a MultiView Monitor from
http://stores.ebay.com.au/loudroomcreations. $135 for the screen and one camera. Post-Christmas, I bought two more cameras ($60 delivered) and I've finally finished installing it.
A couple of issues. First was a DOA camera. The guy was quite contactable and a replacement was quickly on its way. Second was self induced ie. If you have to cut the corrugated conduit you're using to protect the cables, make sure you remove all the cables first
The screen clamps over the rear-view mirror and as it's relatively heavy, it also has straps to help tie it in place.
I've wired it up so that it comes on when accessory power is on. I picked up accessory power from the cigarette lighter and ran it to a fused relay under the bonnet and use it to switch on power from the main battery to the cable normally used to signal the system that the car is in reverse.
The screen can display up to three cameras at once. I have a camera at the number plate, pointing at the towball, underneath pointing forwards (bit of an experiment, it may go) and will put one on the trailer.
I've found the underneath and towball cameras stay clear in the rain but the number plate one mists up. Applying some Rain-x seems to have helped with that.
The underneath on was clouted by something yesterday on the way home from work but I'll give it more time before deciding whether to move it or not.
Number plate camera
Towball camera
Underneath camera
Various views of my untidy garage.
No, I don't know why the underneath camera displays parking guidance lines, it's supposed to be identical to the towball one!