What does this switch activate?

I didn't bother to read the rules, but why would you need anything more complicated than the standard issue taillight(s)?

You didn't need anything else. Just that you remembered you had to turn them on. If you forgot to turn the tail lights on you are DQ. So I wired my back up lights to ignition feed. This way as soon as I turned the key they where on. I ran both so if a bulb went out I had a back up on. Remember they only had to be on at night. Easy to forget to turn on lights.