A growing number of small, inexpensive personal devices measure a person's blood alcohol level, providing drivers with an easier way to assess their fitness to drive.
Experts warn the devices do not guarantee a person can drive safely, The New York Times reports.
The costs for these devices can be as low as $30. Some hang from a key chain, while others are sold as smartphone accessories.
Critics of the devices note they aren't necessarily accurate, in part because impairment from alcohol varies among people.
Proponents note they could be useful for parents who want to check whether their teens have been drinking.
BACtrack sells a hand-held unit that displays a graph predicting a person's blood alcohol levels in the hours to come on an iPhone, through a Bluetooth link. Company owner Keith Nothacker says the device won't guarantee whether a drinker would be under the legal blood alcohol limit, but is simply an education tool.
Device manufacturers say personal blood alcohol testing units will be particularly useful if states follow recommendations by the National Transportation Safety Board (NTSB) to lower allowable blood-alcohol levels for drivers, from 0.08 percent to 0.05 percent.
The NTSB said thousands of people are killed or injured each year by drivers who are not legally drunk, but who are still impaired. Currently about 10,000 people die in alcohol-related car crashes each year.
A person with a blood-alcohol level of 0.05 percent is 38 percent more likely to be involved in a crash, compared with someone who has not been drinking, according to the NTSB. A person with a 0.08 blood-alcohol level is 169 percent more likely to be involved in an accident.
Nothacker told the newspaper that "law-abiding citizens can't possibly be expected to know the difference" between 0.05 blood alcohol content and 0.08 blood alcohol content without doing a test.