Some wire in a 12v connector near the sewer lines; I made a line to run off the trailer's 7-pin connector.
I also bought a clear elbow to go between the macerator pump (aka poop cannon) and the drain so I can tell when the tank is clean. Yes, ew, but very useful.
A note about the backflush port. It will
- allow you to push clear water into the tank to help flush more of the solids out
- allow you to clean out the hose between the poop cannon and the sewer point
- make you think, for a moment, that your tank is sparkling clean (until the water starts to murk up again)
It is NOT a tank rinser. If something is stuck in the tank the flush port will probably not remove it. The best way I've found to do that is occasional use of a spray wand
directly down the toilet (and regular use of the Geo Method