Many newer cars have an engine push to start button. To start these cars, instead of turning a key, you push a button. In order to install one of these for your car you will need a button, some connectors and wire cutters. You will need to know what wires control what accessories, and which wire goes to the starter solenoid. The button will need a power wire to one side. The output side of the switch will need to go to the input of the starter solenoid. A locking two position push button will allow you to power accessories as well as energize the starter.
For more info, see 4 Easy Step to Properly Perform a Car Alarm Installation