I have often wondered why more vehicles did not have that annoying "dinging" sound to remind the passengers and driver that someone in the rear seat had not bucked their seatbelts. It seemed to me that you would especially want this kind of warning system for the back seats since that is where parents usually seat their kids. It’s hard not to put on your seatbelt when this sound is being repeated.
Now Consumers Union is seeking to have the NHTSA require auto manufacturers to have such seat belt warning systems in place. You can read the CU blog entry here. The NHTSA research on such warning systems is found here.
Hopefully this new rule will be adopted by the NHTSA.