I have not used it but the one I saw connects to OBD2 port and monitors everything it does. It benefits the insurance companies mainly. If you accelerate too fast or stop too sudden, or speed/drive aggressive. I have heard that they can even detect steering inputs and blinker use. Im sure all are a little different but it is a black box that I will not subscribe to. I have never been asked to provide mileage proof showing I drive what I say I drive. All my vehicles are listed as less than 5k per year and for pleasure.
09 G8GT, Stryker, sport/prem
08 GXP, Mean, Auto
03 Excursion Limited, V10, 2WD and 37s
94 Bronco XLT, 5.8L, very rusty and 35s
07 GXP, Mean, manual-RIP 1Apr13 @14K miles