07's came w/a 6-pin plug for trailer/toad wiring. In the Owner's Manual, ~pg. 16, there is a photo that shows the pin-outs.
Check them before relying on the photo, as my 08 is reversed (mirror image) of what the photo says; I think it may have been annotated from the view of the electrician wiring the plug from the back, which would be backwards from the owner staring forward into the plug's pins (and likewise backwards from a photo looking at the pins; WRV is going to fix that in the next revision of the Owner's Manual
On the photo, it shows the left-most pin as "auxiliary." You could use that pin for brake controller if a one-wire controller is used. Center post is common ground, which should be made to ground on the toad's side of aux braking system in most cases. Center post may not read ground with key off, IIRC it is set to ground thru the Vansco when the key is switched "on."