Came across a discussion some time back on another board about how to rig a hidden security feature into your vehicle to disable the ignition circut to the coil or starter relay. Could be used if you're like myself & like to avoid having to use keys as well.

From the discussion I came up with a workable diagram using two relays & a flashing LED that can all be had at Radio Shack or another electronics retailer. Can be tossed together by anyone with a basic knowledge of wiring & a soldering iron.

All of the components can be mounted inside a small enclosure & put inline to disrupt the coil wire.

The way it works is this:
The magnetic reed switch is mounted somewhere on the interior where only you know it is, say under a door panel, and is actuvated by swiping a small magnet attached to your keychain over the spot.
A flashing 12V LED is mounted like an alarm flasher that is always on when the ignition circut is disabled. When the reed switch is tripped the light will go out & the circut is armed.
Under the dash can be mounted a simple push button switch that disables the circut.

Materials:
Dual pole, dual circut (DPDT) 12V relay
Single pole, single circut (SPST) 12V automotive relay
Normally on/momentary off push button switch
12V flashing LED
Reed switch, normally open
Magnet