Thus far, I've read nothing to suggest this technology.
It's pretty simple:
The requirements are that there is someone sitting on a particular seat and they are wearing their seatbelt. You want to ensure that the seatbelt is being worn by the occupant to the maximum extent possible.
To do this you need three sensors:
One on the seat to detect weight in the seat, say 50 lbs. or something like that so it can detect if a child or adult is in the seat.
One to detect that the seatbelt is locked in place.
A third could be added to tell the seatbelt was moved from being retracted to being pulled out.
All you need after that is a simple program in something like ladder logic to make things work.
1. There is weight on the seat meeting the requirements for someone sitting in it.
2. The seatbelt was NOT locked in place when that weight occurred.
3. The seatbelt was pulled out after the weight on the seat occurred.
4. The seatbelt is locked in place after the weight occurred and the seatbelt was pulled out.
If you don't meet all four requirements, the alarm goes off. The vehicle does not have to be running to meet these requirements. If the vehicle is not running, the alarm will not sound.
So, if there is no weight on the seat and the seatbelt is locked in place, the alarm goes off.
If there is weight on the seat and the seatbelt was not pulled out after that weight was sensed and locked in place, the alarm goes off.
If the weight is removed, the sequence repeats. You have to unlock and then retract, pull back out, and refasten the seatbelt.
It's all a few lines of code. You could stick it on an 8- or 16-bit chip easily.
This means you cannot leave the belt clipped in place. You cannot use a belt clip as a substitute.