They connect to the ODB port to monitor speed, and braking. From Progressive's site: What information does the device collect? The Snapshot device collects inf

They connect to the ODB port to monitor speed, and braking. From Progressive's site: What information does the device collect? The Snapshot device collects information about how you drive, how much you drive and when you drive. It also collects your vehicle identification number and triggers an email to you if it comes unplugged. Some devices collect location data: this is only for research and development purposes—we don't use it to calculate your rate.