Instead of using an ugly and annoying cigarette lighter plug to power my low-power accessories, I prefer to wire them in permanently and hide the wires. Here's the trick to powering items you want to turn on with the engine like a radar detector. Instead of simply tapping the fuse with a wire, the Add-A-Circuit uses the fuse for its original circuit, and adds a separate fuse for your own wiring.

Parts:
(1) Add-A-Circuit $6.95us from Parts Express
Extra wire as needed

Remove the plastic fuse panel cover from the left side footwell. Use the fuse puller or needlenose pliars to pull out fuse 36. Place the fuse in the add-a-circuit along with another 5A fuse (included with it). Push the add-a-circuit into the fuse 36 socket.

Pull open the shelf under the steering wheel. Run the postive wire up and around the inside and into the area of the shelf. Splice any positive wires with the positive wire from the add-a-circuit. Be sure to cover any bare wire and connections with electrical tape.

Find a screw that bolts to the metal frame of the dash that will be good for a ground connection. Loosen the bolt and connect the ground wires to it, then re-tighten. Verify everything works by turning the key to the full engine on position. Secure any free wires with tape or a ziptie.