Have tried several others but has been the best by far: Haloview Handy 7 Wireless.
It is portable and has a magnetic base so you can stick it anywhere made of steel. I put it on top of the hitch and have converted backing up and hooking up to a one person operation. No wiring.
The one fly in the mixture is the short six to eight hour battery life but it comes with a battery pack that more than doubles that and also has a magnetic base. Range is good, stuck on the back of my 30 ft RV it works fine, supposedly has a 50+ ft range.
Arctic Fox 25Y Travel Trailer
2018 RAM 2500 6.7L 4WD shortbed
Straightline dual cam hitch
400W Solar with Victron controller
Superbumper