I think the camera (s) would be a better option. Get a monitor that clips on over your rear view mirror and accepts input from multiple cameras. Mount a camera on each of the back corners on the trailer and switch between camera views, with the remote control.
Look at the hundreds of listings on ebay. Some of the cameras send a signal with built in distance indicators. When you're looking at something on the screen, you can also see how far it is. Most of them are measured in meters, but, it doesn't take long to get used to that.
There are also listings for video / power cables, up to 100 ft long.
I use one for hitching up my travel trailer. I can look at the monitor and back the hitch ball under the trailer coupler, on the first shot. No running back and forth from the cab, to see the coupler, No having to tell a spotter, "your other left", etc.
I also have one mounted (wired it to be on all the time) on the back of the trailer, for watching traffic and backing up.
This option would probably be cheaper than a front receiver.
