Sitting at a red light at night, I saw a big white SUV getting close in the mirror. I moved up a bit as it screeched to avoid hitting me. I did my normal scream at the driver, but did start thinking; I had my Dowco overnighter bag on my rear rack. When I parked, I tried to get the SUV drivers view of my bike from above. With the Dowco bag, there was no way that he could see my brake light as it sticks out way past, and over the light. As drivers, we do tend to watch the brake lights and rely on them somewhat to know what the person ahead of us is doing.

I would like to install some auxiliary lights to avoid getting rear-ended in the future. Does anyone know if we need a relay, or is it a simple hookup?

Thanks in advance.

If you are going to be adding lights (instead of modifying existing lights as per Paladin), then a simple hookup is all you need.
The mechanical switches for the brakes should handle anything you can throw at them.
Even a temporary light that you plug into a jack then put it on your overnighter bag (velcro) might be ok.  Legal .. dunno about that, but I don't see why not.

I added a aux brake light (LED) to my sissy bar (like a car's third brake light).    It was $9.99 at AutoZone.  I tied it into the brake light wiring under the seat.   Then I realized my backpack covered it up, so I added a connector (AutoZone also) and put another aux lite on the backpack.   I could get more lights & connectors and add them to whatever I want to carry.

Aux Brake light

Rear view
Backpack w/light
Backpack connector

EDIT:  the light is brighter than it appears in the photo's.  My camera auto-adjusts gain so it dimed it.  It is that annoying LED brightness.....

Thanks for the excellent suggestions and links. Knowing that I could just use the existing brake wiring without a relay gives me a whole slew of ideas. Very innovative bunch here. I like the backpack connector idea a lot.

I made my turn signals brake lights too,on my '86.Dual filament aftermarket turnsignals.