As far as I know any sharp tool in the shed could do a killswitch for you. That's just a matter of an open/close circuit on a vital part of the car like the fuel pump, ignition... pretty much anything electronic that would stop your care from starting when the circuit is open.
A good alarm person will install a top alarm such as the m80 mongoose, make sure they mount the control unit in an extremely difficult place to find eg. not in the glove compartment and know what the hell they are doing and be able to run you through everything to do with the alarm.
Daniel came to my house on a Thursday afternoon because he was having difficult fitting me in through the day. Stayed till 10pm to make sure he finished the job and did the m80, tilt sensors, motion sensors, auto window closers and my turbo timer so he knows a good deal of stuff.