without wanting to sound harsh,
ive been to many accidents where people have been catapulted through the windcreen, kids, dads, mums you name it they have all been through one and all because they didnt wear a seatbelt.
I personally think any device which annoys you so much that you are forced to put your seatbelt on cant be a bad thing can it.
lets face it you wouldnt buy a car that has no airbags, abs ets nowadays would you
and yet you would drive around without the single most important piece of safety equipment available !!
Madness imho