Police officers check drivers at a sobriety checkpoint in Escondido, Calif. Lenny Ignelzi/AP hide caption

itoggle caption Lenny Ignelzi/AP

The BACTrack Vio keychain breathalyzer and app on the iPhone at NPR headquarters in Washington, D.C. A public health researcher says tools like this could help people make better decisions about alcohol use. Meredith Rizzo/NPR hide caption

itoggle caption Meredith Rizzo/NPR