It uses a credit card sized keyfob with rfid technology. It has a proximity sensor so whenever you approach the car it unlocks. And once inside you can select acc or ignition on the push start button. A nice feature is you can select a few oem buttons ie a Nissan gtr,s2000, Lexus etc. When you walk away from the car the doors lock and it arms the system. It also comes with two emergency fobs that do not use battery's. You place them over the sensor , usually installed at the base of your windshield, and it unlocks the car and let's you start it. It's a nice system. You can also have a trunk unlock and a remote start option as well.
They are actually having a 50% off Sale this month
http://www.digitalguarddawg.com/