Adjusts the height of the seat belt strap so that it rests just above the shoulder to prevent the seat belt from rubbing the child's neck and to ensure that children do not place their arm over the belt.
I wouldn't say this is a great deal since it is £9.99 for something that probably costs less than £0.50 to make. But having said that, I think it is a good idea and there might be parents looking for a solution for their kids not wearing their seatbelts properly, which could end up in them becoming paralised from the waist down. So £9.99 is good if you consider that it could save your child from serious injury.
You can watch the Dragon's Den clip on http://www.bbc.co.uk/dragonsden/