Brake controller for towing

[sonicsmooth]

2018 XC60 T8 plug-in hybrid.

I'm looking to solve the issue of a brake controller for towing a 3500 lb camper trailer. We have the hitch installed, a Tekonsha 118773 4-way controller, and I need advice for the 4-to-7 way plug for the camper trailer.

The camper 7 way plug requires a brake output. It appears this needs to come from a brake controller. So far all brake controllers appear to be mounted under the dash. Here are my questions:

* Is dash mounting required, or merely traditional? It seems I should be able to ignore it once I set the gain for a particular trailer. So I'd like to see if I can mount it in the rear with the other 4-way wiring controller and not mess up the nice interior with an ugly controller.

* Can the brake controller input take the signal from the brake light in the rear, or must it come from the brake pedal under the dash? This is part of the question above to try to put the controller in the rear.

* For the wireless type Etrailer C51180, this says it uses the phone to set the gain, but it still requires *something* to feed the brake signal. What is this *something* ? There is no mention of wiring in the brake pedal signal in this case.

thanks