(Ron Antonelli/Bloomberg)

It's a big moment for Tesla: Altogether, the company's Model S vehicles have traveled more than a billion miles. For some perspective, a billion miles is about as far as 4,200 trips to the moon. It also adds up to some 570,000 tons of saved carbon emissions, thanks to the Model S's electric battery, Tesla says.

That's a significant, er, milestone — particularly as Tesla plans to expand its fleet with a cheaper, $35,000 Model 3 that could jump-start consumer demand for electric vehicles.

At the same time, it's also a reminder that Teslas and many other cars are constantly collecting information about the way we drive, and sending that data back to their manufacturers. The observations range from the mundane — are you wearing your seat belt? — to more detailed recordings, such as how hard you brake and how fast you drive.

Automotive trade groups such as the Alliance of Automobile Manufacturers and the Association of Global Automakers are developing privacy standards to ensure that any data you share with car companies won't wind up in the wrong hands. Tesla is not a member of either organization, but it does have a privacy policy that lays out exactly what's being tracked:

To improve our vehicles and services for you, we collect certain telematics data regarding the performance, usage, operation, and condition of your Tesla vehicle, including the following: vehicle identification number, speed information, odometer readings, battery use management information, battery charging history, electrical system functions, software version information, infotainment system data, safety‐related data (including information regarding the vehicle’s SRS systems, brakes, security, e‐brake), and other data to assist in identifying and analyzing the performance of the vehicle. We may collect such information either in person (e.g., during a service appointment) or via remote access.

In certain circumstances, Tesla can even pinpoint your car's current location. You can opt-out of telematics tracking by contacting Tesla, if you want. But Tesla warns that if you do so, you'll lose access to any real-time notifications about the status of your car that the company might otherwise send you.

This kind of logging and monitoring is going to become increasingly common as connected cars become their own software platforms. One of the perks of owning a Tesla is that new features keep getting added through regular operating system updates that help keep your car current and competitive with the newest vehicles rolling off the factory line.

But it's also a reminder of how much Tesla knows about us (and you).