This is a question of what is good enough, there are a number of cheap wireless camera systems for sale on Ebay starting around $50, are they as good as the $350 models, probably not, are the good enough to back into a camping space, yeah, although you might want to splurge for the $85-$100 version. I have one of the $60 (this one on ebay http://www.ebay.com/itm/7-TFT-LCD-Monitor-Truck-Bus-RV-Wireless-Backup-Camera-Kit-NightVision-Rear-View-/112274429743?hash=item1a2413d72f:g:r-gAAOSwbYZXcJhP ) which was installed by the previous owner on my Class A motorhome, the bad side is the color accuracy is awful, think one of those colorized black and white movies on TBS from 25 years ago, the image clarity is only so-so and there will be occasional brief analog looking image glitches / static, but it works to keep from running into a tree and is only $60
