The Ravelco is much more sophisticated than a simple kill switch.
Several critical systems are rewired through the Ravelco connector. The "key" they give you makes all of the required
connections to make everything work properly. There is no standardized wiring on their connector. Very solid concept.
A kill switch would be wired into the starter wiring/relay or the fuel pump wiring/relay.
Also effective, but not as comprehensive or difficult to defeat as the Revelco.
If you install a simple kill switch yourself, you could do it for $10 or so for the cost of the switch and the wire.
Done properly, the kill switch is very effective and difficult to defeat.
You can get very creative with a kill switch, for example you could use the horn button to enable the starter relay.
So then you would hold down the horn on the steering wheel to start the car in addition to the Start button.
Then you could add a switch someplace that would re-enable normal horn function. Just one idea.
ETA: You can do the horn kill switch pretty easily, but here's the "deluxe" setup. No horn when you start, and horn
works as normal after the car is running.
Starter Interrupt Relay Diagrams