Marty Williams recalls the conversations he and his wife would have with their two daughters about the dangers of talking and texting while driving.
"It's always a concern," said Williams, who lives in Howard County, Md. "We just drilled it into their heads over and over until they said 'OK, we get it,' and when we saw something [about the dangers of drivers texting] on TV, we made sure they saw it, too."
Parents like Williams have good reason to worry.
Half of teens say they talk on a cellphone while driving, a third say they swap text messages, and almost half say they've been a passenger in a vehicle with a teen driver whose phone use put them at risk, according to federal statistics. Teen drivers are more likely to get into a fatal crash than anyone under the age of 80, in part because their brains are still developing the system that evaluates risk.
These days, however, there's an app for that, several of them, in fact. There are apps that prevent mobile-device use while driving, and some of them alert parents or employers when a user tries to beat the system. They've emerged on the market as alarm grows over the carnage caused by distracted driving.
More than 3,300 people die and 420,000 are injured annually in crashes attributed to distracted drivers. But those numbers may be low because, other than a driver's admission of fault, it's a challenge to prove that distraction caused a crash.
Among all drivers involved in fatal crashes, teens were the most likely to have been distracted, National Highway Traffic Administration data show.
"They feel invincible," said Jurek Grabowski, director of research at the AAA Foundation for Traffic Safety. "They have large social networks and they want to stay in contact with them."
Conversations on the go, texting, surfing the Internet and taking selfies are such a habit among teens that studies show they underestimate the risk. Teens make up a significant percentage of the approximately 660,000 drivers who are having phone conversations or manipulating electronic devices while driving at any given moment during daylight hours in the United States.
And most teenagers who chat, text or surf while driving are breaking the law.
The District of Columbia and 37 states ban novice drivers from talking on the phone while driving. The District and 43 other states bar all drivers from sending and receiving text messages while driving. But respect for those laws is akin to that given the speed limit.
"We need to almost turn this thing into a brick," David Coleman said recently, holding up his cellphone while sitting in a Bowie, Md., Starbucks. "It can't just be about texting. It has to be about email, Facebook and no inappropriate calls."
Coleman is marketing director for Louisiana-based Cellcontrol, one of several companies competing for the chance to shut down people's mobile devices while they're driving. Most of the companies that sell cellphone service -- Verizon, AT&T, Sprint and others -- also provide apps that can limit access.
Many of the apps are triggered when a GPS sensor detects that a vehicle is in motion, and some -- such as AT&T's DriveMode -- will alert parents or employers when the app has been turned off or disabled. Independent experts consider that a feature buyers should look for.
"Especially for younger drivers. As clever as you can be, they will be more clever," said Leo McCloskey, a tech guru for the Intelligent Transportation Society of America.
"The best way to do it is to integrate the device with the vehicle so that you could have more fine-grained control."
That fine-grained control means that parents or employers can select the features they want to allow their drivers to use and block those that worry them.
"It's important to have a solid oversight function so that use can be monitored by a fleet manager or parent," said Russ Rader of the Insurance Institute for Highway Safety.
"Cellcontrol is one of the better, most complete systems. TeensSafer is another one that we've looked at that works pretty well," he said. "These products are going to be the most useful for fleet operators and for parents trying to control phone use by their driving teens. Both Cellcontrol and TeenSafer will report attempts to tamper with or override the system."
Businesses that send fleets of cars, vans or trucks onto the streets have shown increasing interest in those products, as juries have issued multimillion-dollar rewards to those injured or killed by distracted drivers who were on the job.
Systems integrated into the vehicle are triggered when the car or truck begins to move.
"We're not guessing based on a satellite, we're depending on the vehicle to tell us," said Cellcontrol's Coleman as he spent a morning demonstrating his company's product In Prince George's County, Md. "Otherwise, how do I know you're not on a Greyhound bus or on a plane that has landed and is taxiing to the gate?"
Cellcontrol provides two options for connecting to a vehicle. One is a device the size of an electronic toll transponder that is glued to the windshield with the same adhesive material used to secure rearview mirrors. The more sophisticated choice plugs in to a vehicle's diagnostic computer port. The $129-system works with iPhones, Androids, BlackBerrys and Windows Mobile.
The system involves an app that is downloaded to the phone of the driver -- teenager or employee. The key to the system is software that can be installed on a home computer, tablet or mobile device that allows an authorized person -- parent or boss -- to customize what the driver is permitted to do, and to monitor compliance.
"We're not blocking the signal, we're allowing a protective policy to be brought into the device," he said. "The administrator has the option to make the policy as restrictive as possible, or not."
For example, phone use could be restricted to a hands-free device. Or calls could be restricted to an emergency number or a parent or office.
Or parents could attempt to mandate that all passengers in the car driven by their teenager download the app.
"You could decide this is the kids' car and we don't want knuckleheads sitting in the passenger's seat showing the driver YouTube videos," Coleman said.
Coleman demonstrated how his phone was preprogrammed to go into safe mode when he drove, but when handed to a passenger it was fully operative. A second phone he brought along went into safe mode when the car was moving, regardless of whether it was in his hands or those of a passenger.
Acknowledging that parents are dealing with a technology-savvy generation and that employers exist in a technologically smart world, Coleman said, "We've built in some traps and fail-safes to notify the parent or employer."
McCloskey said that companies such as Cellcontrol that provide integrated services are "where we need to go."
"The operating system of the phone itself can interact with the operating system of the vehicle in such a way that services can be authorized, services can be presented, and services can be consumed all in a safe and predictable manner," McCloskey said.
Although he is concerned about distracted driving, McCloskey thinks it is a relatively short-term problem.
"The irony, frankly, is that in the medium to long term, as autonomous vehicles really start making a mark, all this goes away as a concern," he said.