I took part in the Progressive program (Snapshot). Had devices in four cars for about 3 months. I got an extra 15% discount for my sol ($124.00/yr); total savinigs on all four cars $208.00/yr.
Unfortunately, my wife had long commute at that time so she only got a 6% discount. Right after our 'trial' was up, she lost her job so didn't put hardly any miles on her truck after that. Timing is everything!
Been awhile but I know they track speed, sudden stopes, how many trips a day, and time of day driving. The cars are tracked 24hrs/day. You can go to the website and see graphs of your usage. Was kind of neat but happy not to have them installed anymore. I hated having everyone pass me on the freeway.