There's no question it monitors whether the seat belt is buckled. I
haven't seen a 2006 in person. I assumed by your question previously it
had some sort of occupant classification system, but I don't know that it
does. The air bag system will not conclude someone isn't in the seat just
because someone isn't buckled. It does use that information in determining
whether to deploy the air bag. In fact, it's more likely it will deploy
the air bag if the belt is unbuckled. I recently worked on a Tiburon that
(if I recall correctly) fired the driver bag but not the passenger because
the passenger seat belt was buckled and the driver seat belt was
unbuckled, so the system felt it necessary to deploy the air bag to
protect an unbelted driver. If you want to know, check out a car in
person. If it has the passenger air bag telltale, it definitely has an
occupant classification system.