Two ways:
right way = specifically designed unit that has a shutdown process
wrong way = bypass clutch, no shutdown process
Both systems will require you to actually bypass the clutch but the right way will require you to leave your vehicle running when you exit and the drivers door closes (signal required) they car may be shut down. It monitors certain zones on the car, and if they are violated then the car wont start.
Polar start, clifford, nordic start, DEI (soon), auto start, command start, and a few other make models as well.
Word of warning to all those that have it the wrong way:
If your car ever jumps forward and hits someone, be prepared to spend time in jail as well as pay the person you hit for the rest of your life. And if you think it wont happen to me, think again, I see a couple examples of this every single year, and vehicular assualt is not a pretty charge.