I wondered that too when I was installing mine so I opened up the cigarette lighter plug and found only a fuse (there's one in the line too) and connecting wires. Just 12 volts all the way through.
Ok, awesome. I was hoping I'd find someone who actually took the time to do that. Thinking about tapping into my rear view mirror on my truck, but I hadn't ordered it yet. Any chance you know what amperage those fuses are rated?