Wow - I don't want to get into an argument about semantics (you were the one who used the word "progressive") and it's apparent you are convinced what you know is the last word. Sorry - I've towed so many different vehicles in the last ten years, from very lightweight Scions to 8K lbs diesel crew 4X4 pickups, and lots in between. And I've used the RVi brake for so many of those, under so many conditions - all behind a diesel pusher though so my experience does have that caveat. And, I've gone down LONG steep grades of varying slope - all the while my RVi has braked the way it is intended - progressively, and applying the brakes when I tap the brakes in the coach. But maybe you're not aware that braking is done a little differently in something with air brakes - and that action does indeed apply the toad brakes with the RVi. But let's not throw the Patriot in there - that device uses a whole different technology, and shouldn't be compared to a RVi brake. As for the Invisibrake vs. RVi - I'll stick with my RVi thanks.
You can puff your chest as much as you wish. I purchased the Ready Brake, Patriot 3 and the RVI all last year and tested each one over a mountain pass that we travel every time, all were crap. By the way the RVI does not even engage with a tap of the RV brakes it takes more significant braking to engage and that is consistent with all three mentioned above. Having used and experienced all three is the exact sale location and situation you can take my summary or NOT. I even called RVI as they claimed it was progressive, however when I challenged them regarding how it braked on long downhill descents they admitted that it is not always a progressive braking system it depends on the descending or stopping conditions. While it is good at stopping both the Patriot and RVI are not great at simply slowing down on long grades as there is not enough inertia change to engage these systems. There is a reason that Invisabrake is the #1 used and recommended braking system it is truly a mirrored braking system whereas wireless system are not capable of. Again this was my conclusion after towing with all of these and then looking at all options both wired and wireless.