I guess if neither you or your fishing partner can back a trailer up, you might need this. Me I'd rather spend the extra money on fishing accessories.
Hell in fishing for 20 years in the Pacific I've only backed my boat in a handful of times. Someone else backs it in and I'm at the helm and back it off the trailer and when we load some one else backs the trailer in and I drive it on. And nobody but nobody should go out in the Pacific alone!