You're talking about the beep/chime/bip when you drive with the drivers seatbelt unbuckled? Or does yours do that for the passenger seat if you put something on it?
I'll have to try to see if I can shut that warning off. If I move a car across the parking lot(not wearing a seatbelt) it'll start chiming away and won't shut up until you either shut the car off or buckle the seatbelt. It still goes off once stopped and car is shifted to park.
I'll try to mess with that when I get a chance, Maybe later today?