we have the M&G
brake system on our coach/toad combo which ties into the air brakes on the coach to provide proportional braking on the toad. Works a lot better then our old "brake in a box" system we used to use.
One drawback to this system is it is not compatable to all toads but I checked the list on their website and Outbacks up to 2012 are listed but nothing for the 13's. The list was last updated on 4/2013 so they may have more up to date info if you call them.