Ford device to slow down the kids

Ford is on the way to marketing a device in America which will allow mum and dad, sorry that's maw and paw, to control the maximum speed of cars driven by their offspring.
Models in 2010 will be offered with a computer chip limiting the car, on selection, to 80mph.
On the face of it a good idea. But a couple of points arise.
80mph, like a foot of water, is plenty enough to kill. And there is a cheaper way.
Just have a little fiddle about with the timing and even the most determined teen won't get their Ka beyond 60mph. Don't worry, like cleaning bedrooms, it is almost unknown for Kevin or Perry to look under the bonnet Sorry, hood.