I have been reading about experiments with these for years, but first noticed them in european brochures only a couple of years ago. I haven't read any user reports as of yet, but then again, I haven't really been looking for them.
THey are actually produced by the chassis manufacturers - ALKO being the most prevalent, so they should be available for most caravans. ALKO produces about 90% of european caravan chassis.
Here is a YouTube link to the system as used in Australia: ALKO ESC (Electronic Stability Control) 2012 - YouTube
These systems work by applying the trailer brakes
independently of the tow vehicle. One could argue that with our electric brake controllers we can simply reach down and apply the trailer brakes, but these systems react far more quickly than we can, and when we are fighting for control it is difficult to pull a hand from the wheel to control the trailer brakes. As for using the vehicle and trailer brakes by applying the foot brakes, as the driver in the video points out, sometimes that is the worst thing we can do.
Let me know if you find any user experiences out there.