SAN DIEGO -- A tiny new device tracking the car's every move may save drivers money on car insurance.

But there's a catch: drivers have to let the insurance company become a backseat driver, of sorts.

It's called the "TripSensor", developed by Progressive Insurance. The device measures when people drive, how far and how fast, and depending on those factors, the customers could get a 5 to 25 percent discount.

"Progressive's interested in this because we know people who drive less are less likely to have an accident. So, we give them more of a discount, they present less of a risk to us," Progressive representative Jim Haas said.

Currently, thousands of drivers in Minnesota are participating in a pilot program.

"The program is entirely voluntary, you don't have to do it if you don't want to. You get to look at the data before you share it with us and decide then [whether you want to share it.] If you don't want to share it, that's fine," Haas said.

And privacy advocates -- including Beth Givens, the director of the Privacy Rights Clearinghouse -- likes that.

"Progressive has appeared to put the subscriber in the driver's seat," Givens said.

But she still has some serious concerns.

"Not only could the privacy policy change at any moment, but there could be demands for that data from third parties," Givens said.

Givens said the records could possibly be subpoenaed in a custody battle or by law enforcement, making personal driving data public record very quickly.

When it comes to sharing any information with companies, the Privacy Rights Clearinghouse recommends drivers read the privacy policy and terms of service very closely.

The pilot program will last at least a year.