Garmin has a couple models that will accept input from a rear camera. Both models are in the larger 7" screen size.
Garmin has dramatically expanded their lineup of devices that are capable of backup cameras since I last looked into it a year ago. Their are many models. This one below comes with garmin own backup camera setup (Wireless, and expensive when bought separately). You can use a normal wired input camera for a lot less, but you will need an additional video adapter cable. http://www.amazon.com/Garmin-2798LMT.../dp/B00FMUYYZA
After researching this more, it's clear that most of the Garmin models available now will only work with garmins own BC30 camera setup ($150). You could look for a refurbished Nuvi compatible with the BC30, several refurbished are under $100 on Amazon. They are a great way to save some coin on a garmin.
The models that accept a wired camera are limited to the older Dezl and RV models. I don't see any refurbs of those for less than $225. They all utilize the BC20 camera, but also have a video input jack.