I'm doing an install of an Appradio 3 in my 2003 Ford Expedition and I need a recommendation for a backup camera. I know there are some cheap solutions on EBay that work, but I'm not sure which one to get.

I'm using my old Kenwood CMOS-200 backup camera I had with my previous stereo.   Looks to be over priced still even 3 years later.  

If you pick any of the low cost eBay option let us know how well it works.

Mine was 16quid from china! Via eBay uk, works great

Any camera marketed as a back up camera will work. No offense to leetut but stay clear of cheap eBay cams. Total Chinese garbage with about a 50-60% failure rate or very short life and no practical way to return them if defective or short life. 

An economical camera with a decent quality and reputation is BOYO.

I bought the cheap one that mounts on license plate on Amazon for $16. If I have a problem I'll upgrade to a direct fit model that I found for my expedition.

Again, if its made in China with no brand name its likely going to have an exceptionally high failure rate.

I had a cheap $19 one I got from Amazon. It died after its 2nd car wash. I've been using my new camera for well over a year now without any issues. It was only about $38 IIRC. It's a Crimestopper model SV-6818.EM I believe.

http://www.crimestopper.com/index.html