Auto insurance is a thing, and OBD-II diagnostic plugs are also a thing. Metromile brings these two things together in a marvelous fusion of data and pragmatism. With the new Android app, you can get diagnostic data out of your car and take advantage of Metromile's insurance rates based on how much you drive.
The service is currently only available in California, Oregon, Washington and Illinois. If you are lucky enough to live in one of those locales, the "Metronome" OBD-II device is free. Simply plug it into the port under your dashboard, and the app will return information about how the car is working. You can buy devices like this on Amazon (ex. Automatic) with apps on Android that receive that data. Metromile is basically the same thing, but with optional auto insurance attached.
The idea is that you'll want to buy insurance from the company because it's usually cheaper. Since the OBD-II can feed driving information into the app, Metromile knows how much you're driving instead of ballparking it, thus making the rates lower. If you aren't in a supported area, you can sign up to be notified when and if the company starts offering insurance in your state.