That could be an interesting solution. (But wow, what a price.) When you think about, that's really a great way to handle trailer breaks: no matter which tow vehicle you connect to, you have brakes on the trailer. I wonder how they detect a brake pedal push in the tow vehicle - or maybe they don't and just assume that any deceleration calls for braking? (Which would probably work OK with a proportional controller in over-the road situations.)
The only downside I see is that it's a proportional controller. I greatly prefer proportional for over the road towing: it gives much smoother operation than the time-delay based brake controllers. However, proportional controllers can be a problem for off-road use: the rougher the terrain, the more they get confused. This is why time-delay based controllers tend to be more popular with off-roaders.
I installed the Redarc Tow-Pro Elite controller in my antique military pickup: it's used both on-road and in the woods. The controller has selectable modes for proportional or time-delay control. (It's also the one I referred to earlier which the box installs remotely with just a knob on the dash to control.) Not weatherproof, unfortunately.
I had it "thrown in" among other things after getting total price, but I'd be surprised if the kit (brackets, plugs, wiring) was over $60 and as far as installation, plug and play, bet it was installed in 5 minutes and took longer to unbox it and take the plastic off it than install it.