[Mahh]

If you're interested becoming afraid around your cars, some of my security friends at the University of Washington have been busting up cars for research: http://www.autosec.org/faq.html

This paper is particularly in depth and interesting: http://www.autosec.org/pubs/cars-usenixsec2011.pdf

Of course, their exploits are a bit more complex and involve various side channels and hardware vulnerabilities, while the keypad issue can be executed by someone just typing in numbers with their fingers.