One in four American teens of driving age says he or she has texted while driving, and almost half of all youths ages 12 to 17 say they have been a passenger while a driver has texted behind the wheel, according to a survey released in November by the Pew Internet and American Life Project.

So when Darcy Ahl's 16-year-old son tried to answer his phone while driving, she was rattled to the core. The car started swerving on a busy interstate, and Ahl frantically instructed her son to end the call.

"I wondered to myself what would have happened if I hadn't told him to hang the phone up," Ahl said. "I wondered what would have happened if I weren't there."

Immediately after that scare, Ahl, an executive recruiter, went back to her office to figure out a way to keep teenage drivers away from their phones. By the following morning, iZUP's concept was completely formulated in her head.

Ahl came up with an idea for a smart phone application that prevents drivers from talking on the phone and texting while driving. Illume Software is releasing the application iZUP today. Ahl co-founded Illume Software and is now the company's vice president of public affairs.

The application iZUP uses GPS technology to detect a car's speed. If a car is traveling over 5 miles per hour, the application sends incoming calls to voice mail and holds text messages. It also blocks outgoing text messages and calls, except emergency 911 calls.

Account holders have the option of entering authorized phone numbers, such as parents' cellphone numbers, that the driver can both call and receive calls from while en route.

The application is teenager tamper proof, according to Illume Software. It is difficult to improperly uninstall, and if it is successfully uninstalled, the account holder will immediately receive an e-mail alert.

I downloaded iZUP onto an Android G1 phone and tested it out. While the car was in motion, iZUP held my phone hostage. It didn't allow me to do anything but call authorized numbers.

The application prevented texts, phone calls, Internet use and denied me access to my contacts and music ... even when I was sitting in the passenger seat.

An Illume Software representative said that the account holder can enter a pin code that temporarily disables the application if, say, his or her teen will be a passenger on a long road trip and wants full phone access.

The application worked as intended, but there was about a minute-long delay before it recognized the car's speed and either worked or disabled. A few times the lag enabled me to make and receive phone calls while the car was in motion.

But as soon as the application recognized that the car was traveling over 5 miles per hour, it shut down all communication. When the application kicked in, I was not able to make outgoing calls, and when I tried to answer incoming calls, I'd hear music instead of the caller's voice.

Copyright © 2009 Tribune Company. All Rights Reserved.

Copyright © 2009 Tribune Company. All Rights Reserved.