These insurance box's don't just check how many miles you drive, but also record how fast you drive, rates of acceleration and braking, cornering forces and also time of day and length of journeys to gain an overall picture of how you drive. If you drive sensibly, then they can be a real bonus, particularly for young drivers, to getting your premiums down.
If you're going to drive it like you stole it, then you're premiums are most likely going to go up. The question for you, is are you willing to drive like an angel to get your premiums down or are you willing to settle with slightly higher premiums and the freedom to drive how you like?