I have 2 Wi-Fi cameras that I use, but only while on the road for the blind spot in back of the TT and for hooking up. They are good to over 300'. Do not look at the license plate cameras, as they lack the needed RF transmitting power. Wired in units are a good selection.
As for backing up, DW does a great job guiding me. When I start backing up into the spot, I stop and get out to do a walk around. I look for any low hanging branches, where the table is, where the fire pit is, and any other obstacles.
I then walk over to the Electric pedestal and water pipe, take my arms length from the Electric pedestal (slide out space) and make a grove in the stones to mark where I want my tires to follow. If it is a paved slab, DW will stand back and in line where the TT's tires needs to follow. The DW usually just lets me know how far back to go, as I am usually a couple feet short.
I mostly use the mirrors, but it is a second line of defense having DW jump up and down swinging her arms and yelling, should I miss my mark. We sometimes use our smart phones to talk to each other while backing in.
2013 Jayco Eagle 284BHS
250Watt Grape Solar Panel, MorningStar MPPT 60 Charge Controller
1500 Watt Ramsond PSI, 2 Trojan T145 Batteries (260Ah)
2 - AirSight Wireless IP Cameras (used as rear view cameras)
EnGenius WI-FI extender, D-Link wireless (n) modem
MagicJack Internet Phone
2012 Ford F150XLT, EcoBoost w/3.73
157" Wheel base, HD Towing Package
Our Solar Album http://www.jaycoowners.com/album.php?albumid=329