I use the Draw-Tite Activator II Electronic Brake Controller, it's been around for a long time and most important to me was that it can be mounted in any angle unlike many controllers out there. The Tekonsha P3 is a sweet unit, not sure if it can be mounted at any angle though. If so, it would be the way to go.
I mounted mine sideways on the left side of the console using Velcro. When it's not being used I can easily remove it and tuck it under the dash where it's sight unseen and out of the way.
I have the installation instructions for my Activator II posted in my library if you care to it.