Has anybody had a "Smart Box" fitted to their car?

Im just looking at quotes for car insurance with the Co-op, and just wondered if anybody has had a Smart Box fitted to their car? I think its a good idea, but just wondered if anyone has experience of their premium going up, if so, is it a hugely inflated price that it goes up? Fair enough that it goes down if you drive safely, but can't find any information on how much it'd be likely to go up if not!! Any other info much appreciated! :)