it looks like step-down dc-dc controller:
http://www.ebay.com/itm/12V-to-5V-2A-DC ... 27ce66b2d1
with transistor (probably NPN) and some chip (dont know for what is usefull)..
Principe: When ignition switch is on, Gpio = HIGH, When ignit. is turned off, GPIO = low, rpi is shutting down (you can do with python code), while rpi is turning off, capacitor is discharging, and after discharge, rpi is disconnected.. maybe one diode between ignit. and capacitor could be good because capacitor could discharge wrong way, and much faster...
free alternative looks like: