I wanted to share how I wired a kill switch on my '98 cherokee.

I wired the switch to interrupt the NSS park/neutral signal wire (black/ white on my 98) so that the jeep won't even crank when the switch is flicked. It tricks the system into thinking that the jeep is in gear, and it won't power the ignition relay. This wire is also easy to find (NSS connector near the tranny dipstick) and easy to run a wire from into the cabin (I went through the firewall plug near where the steering shaft pokes through).

I hid the switch inside the cigarette lighter adapter, which I think is a pretty sneaky spot.

I used a flip toggle switch, but a button toggle switch would work better. To remove the heating element from the cigarette lighter, I drilled into the back of it after removing the connector; once the rivet was drilled out, the heater element fell away in two pieces, leaving the housing intact to bolt the switch to.

After that, it was as simple as soldering the wires from the NSS wire to the switch, putting everything back together, and preparing my mad scientist laugh for any would-be thieves!

Hope this helps anyone looking to do the same, and I am happy to answer any questions.