The ASD (Automatic Shut Down- $30.00 words meaning "MAIN") relay powers up lots of stuff on a Chrysler. Coil, injectors, field windings in the alternator..... I cut into the wire from the control circuit of the ASD relay to the ECU for the small terminals of the kill switch. Upsides- you kill the alternator field immediatly, so no voltage spikes to harm your shiny Mopar performance ECU. There is also very little amperage on the control circuit, so your kill switch should last for many happy years. If this doesn't make sense, I can check the wiring diagram and be more specific on colors- its been a while since I set it up on mine.
Edit: Have I answered the correct question, or are you just wanting an on/off switch?