The Verizon Hum, a cute-sounding gizmo that brings safety and diagnostic capabilities to your aging hoopty, just became your teenage son’s enemy.

An update rolling out to Hum owners this week offers some much-requested improvements to the GPS functionality. One key feature: geofencing, which will let a car owner instantly locate his or her car, or receive an alert if it drives out of a specific area — say, a 1-mile radius of your son’s high school. Worry that he’s drag-racing just off campus? Another new feature is speed alerts, which will ping you should that ’07 Honda Accord you gave him exceed a set limit.

“I have a teenager, I would like this,” Michael Maddux, Director of Product Development at Verizon Telematics, told me.

The company aims to breathe new smarts into America’s dumb fleet of cars with the Verizon Hum, which adds electronic brains to any 1996-or-newer vehicles for just $15 a month. Hum plugs into a car’s ODB-II port, the same connector used by a service technician when you come in complaining that the check-engine light is on. While many gizmos have offered to read codes from the ODB port in the past (just search for them on Amazon) the info they convey is usually hard to parse. Hum makes it easy by offering human translators.

The Hum device consists of two parts: a dongle to connect to your ODB port, which includes a cellular antenna and a GPS chip, and a clip-on visor module that looks not unlike an old-school radar detector. The visor module has a speaker, and communicates with the dongle for hands-free calling. It also ties directly into Verizon’s new call center: Push its blue, customer-service button for roadside assistance and diagnostic help from ASE-Certified mechanics trained to tell you what those obscure codes actually mean.

While Hum has offered peace of mind to owners, the new features add practical functionality that users will likely appreciate. Verizon is also offering a new vehicle health report, a monthly email summary containing average mileage, fuel economy, any alerts that popped up, and so on.