I have a Progressive Industries HW50-C. That is HW Hard Wired 50 50Amp C Their code for the remote display.
Being hard wired, it is permanently installed and can not be forgotten or easily stolen at a camp ground. The remote status display is in my "control center" just inside the door, so it is very easy to check the status when connecting power at a campground.
It gives a continuously rotating display of voltage on both L1 and L2, current Amp draw on each leg, Frequency, or Hertz, and any error codes.
I am told the unit has a lifetime warranty with no proof of anything except ownership. I have not had a need to find out.
It is very inexpensive insurance