I, personally, would stay away from wireless systems. Unless things have changed a lot since I last researched camera systems, reception range can be problematic. Night vision and voice are nice touches. Reversible vision on the monitor is a must. I'm not sure what is currently available so I can't suggest any makes or models.
Happy Camping! ///// Richard D.
2006 4x4 Ford 250 SD / 2007 Flagstaff 827 FLS
One very patient wife and one furry child who travels with us. Forty-two years of trailering and camping, and I still have a blast.