As we wrote last week, there are some drunk drivers who knowingly and repeatedly drive drunk but do not care or try to stop. These drivers present a particular problem for Tennessee law enforcement as well as other drivers on the road.

But then there are those who may accidentally drive drunk because they did not know they were over the limit. These drivers can nonetheless cause a serious car accident. But like many of life's problems, there is a smart phone app that may provide a solution, and it was invented by a fellow Tennessean.

A Nashville man and some of his friends created an iPhone app that they say can effectively measure a driver's blood alcohol concentration (BAC) in a range from 0.02 percent to 0.17 percent. Called BreathalEyes, the app uses the phone's camera to scan a driver's eyes.

When someone is intoxicated, their eyes may jerk involuntarily, which is a phenomenon known as "horizontal gaze nystagmus" (HGN). By taking and analyzing a series of photographs, the app attempts to detect HGN and use it to calculate the user's BAC.

The test is similar to the way a police officer has suspects follow a pen with their eyes during a field sobriety test. In fact, this was apparently what inspired the Nashville man to invent the app in the first place.

One of the business partners who helped create the app stresses that it will not tell a user whether or not they should be driving. Rather, it is a tool to help them make a smart and informed decision.

He adds: "I know firsthand that any little bit of information you can put in front of somebody's face to help them make smarter decisions, especially people who have a tendency to abuse alcohol, can help."

Source: Insurance Journal, "Drunk Driver Test? There's an App for That," Jan. 4, 2012