Well at one time it was kind of strange for an economy car to have a passenger side airbag. Now they are standard (required) on every car. Its the same idea, as a couple other folks have pointed out. Here's a link that does a better job explaining than I ever could :-)

http://www.theautochannel.com/news/2...28/060025.html

 

My 08 has it, the person who i got the car from way over inflated it . the warning light came on and notified me that something was wrong. I checked and the tirepressure was extremely high. Saved me from a possible blowout