I hereby proclaim this button to be the "chick-magnet" button.
There are three values, 0, 1/2 and 1. As the name implies, the car functions as a chick magnet when the button is pressed and moved to position 1. This results in all chicks within a certain radius to be attracted to you. when the button is at half, the radius is reduced to close vicinity. 0 means you're with your wife/girlfriend (who have no choice) and thus, no magnet is required
On a serious note, its not stock for sure!! Maybe some sort of air ionizer/cleaner etc...