I don't use it so I should just shut up . . . but . . . . . . . . . . . . . .
I googled it and it seems to be a lot of money (~$170) for something unnecessary.
I set my TT up this way when I first got it:
Spent a lot of time with several levels (6" torpedo, two foot and four foot) leveling the trailer in the driveway. I checked and checked inside and out - - the frame front and back (both sides), the A-frame, the floor inside, the kitchen counter, the dining table, even inside the frig).
Then I attached six levels like these:
https://www.amazon.com/Camco-25523-S...294693275&th=1
one at the front and rear corner of each sidewall and one in the center of the front and back caps.
I use the Andersen levelers:
https://www.amazon.com/Leveler-Ander...124707035&th=1
so when I back in a quick glance at the front level tells me how close I am side to side. I can usually get pretty darn close (sometimes a jog or two back or forward, admittedly)
When unhitched and using the tongue jack, a quick glance at one or both of the front sidewall levels will show when the trailer is level front to back. If any fine tuning is needed it can be accomplished as I deploy each stabilizer at the four corners, and there is a level right in front of my face at each location. Never seems to take more than an extra half turn to even things out, if needed.
I can be leveled out in just a few minutes. The important part is in leveling the trailer at the beginning and in careful, accurate attachment of the levels.
I was a carpenter for 40 years and used spirit levels nearly every day. If they are not abused they can remain accurate for almost forever. Unless they are physically bashed somehow. Mine have been in place for going on 10 years and are still accurate. The bouncing around during travel hasn't affected them at all.
And six levels and a tube of caulk only set me back about $15, and few hours time.