I have used a BetterWeigh with my 2019BE for almost a year now. Does it work? Yes, to an extent. For tongue weight, it just monitors the change in angle of the vehicle before and after lowering the coupler onto the ball. I did not find it accurate or convenient enough for tongue weight use and now use a Weigh Safe adjustable ball mount with scale (a subject for another review...it's good, but only accurate over about 350lbs).
For the weight of the trailer (or actually the overall weight of the vehicle + trailer) it's a useful product. For overall weight I've found running the test (which involves finding a straight, flat section of road where you can stop and accelerate to 15mph) 3x really gives a more accurate idea of your weight, within 10% or so.
I'm guessing you're dealing with an RV; I am not, just utility and equipment trailers that change load every trip. This may change how useful it would be for you...or might not!