irokin: Generally, you'll need a killswitch inside the car within reach of the driver, and for more serious stuff (like circuit racing, targa events and I suppose if your car is very quick down the drag) you'll also need to be able to switch it off from outside, in case the driver is unable to turn it off himself. Most of the time people run a cable (like a bike brake cable) with a loop on the end to outside the car. This goes to the switch inside, so you still only need one switch. Then if you stack it and you can't turn it off, someone can come up to the car and pull the cable, which will turn the switch off.
Some cars do run two separate switches, some have a switch that can be electronically triggered (relay?) so there's a button on the outside of the car that trips it.
Lots of methods. For a daily, probably not required, but never a bad thing to have. The only thing to watch is if you have an external one, try to have a way to "disable" it or tuck it under the bonnet or something so that tom, dick and harry don't keep turning it off everytime you park your car somewhere...