I have a gator one though it's not a rear vision mirror one, it's a separate screen on the dash. After one child ran across a car park one day when I was reversing I saw her in the screen and was able to stop, if I didn't have the camera there's a good chance I wouldn't have seen her. Worth every cent.
Wireless ones suffer interference from several sources, one of which is wireless networking signals, if you or your neighbours have a wireless network in the house they can make it annoying to reverse in your own driveway.
OOOhhh maybe you inadvertently hooked into someones webcam and you were seeing them do something naughty.....or maybe not.