I think it's a good idea if it produces better, safer drivers. In that case I think it should be available to everyone, not just teenagers. There's a lot of adults who have plenty of experience driving, but still break the law, sometimes without realising it.
This kind of device would be better used, I think, as a simple warning system when one speeds, or does something else detectably illegal, rather than being a tracking device.
I've had my licence just over a year, and I am very grateful to my parents for trusting me enough to drive their car. However I know I make mistakes, and it would be very helpful to be reminded if I go over the speed limit, run a red light, stuff like that ... it's a big transition from driving with an instructor or parent to driving on your own, and some people I know seem to forget what the rules are when they drive by themselves.
However the device as it is now couldn't do an on-the-spot warning, which is a bit pointless. I'm not opposed to the idea because it would promote safety, but I think it should be applied to everyone, not just teenagers.