He immediately identified an engineering hurdle: To shut down a driver’s phone, you have to know that the person is driving. “How do we know the person is driving and not riding a horse or is a passenger on a bus?” he said. “How the heck do we do that?”

At the point when Mr. Tibbitts was starting to tease out this puzzle, a handful of technological attacks on distracted driving were already emerging. But they weren’t, and still mostly aren’t, able to answer the question that he was asking. Generally, these systems work by using a phone’s Global Positioning System capability to determine whether the phone is moving, say, more than 10 or 15 miles an hour. If the answer is yes, a screen pops up that allows the phone’s user to override the service if he or she isn’t the driver. (Of course, a driver can lie and thus bypass the system.) Another disadvantage of GPS systems is that they generally eat up a ton of battery life, experts said.

In January, in a parking lot in Boulder, Colo., Mr. Tibbitts huddled in the back seat of a 2002 Mazda Protégé to show off his solution. The car belonged to his son, Ryan, 20, who sat in the driver’s seat. Ryan reached to his left and pulled out a small square box that had been plugged into a port under the steering column. The port, called OBD 2, comes standard in cars built since 1996, and the black box plugged into it is part of a booming business called “telematics” — so named because it combines telecommunications and mobility. Ernst & Young predicts that by 2025, some 88 percent of new cars will have telematics and thus become so-called connected cars.