I've been using the belt for a week now after getting increasingly uncomfotable with the normal seatbelt, and I'm impressed. Wasn't sure exactly what was involved but actually it's a simple device - a flat lightly padded square of material you sit on, fixed to the chair with a belt around the back to stop it moving when you get in. There are 2 velcro attachments at the front which you use to clip over the normal seatbelt at your thigh level which hold it lower than usual.
In the ice/snow recently it's felt much safer to be held in by a belt that wouldn't put tight across my bump in case of an accident, also doesn't press on the bladder which is marvellous! Takes about an extra 10 seconds to fit over the normal belt each time you get in but well worth it. A good buy.