BACtrack (Free)

This innovative app pairs with BACtrack's line of police-grade smart breathalyzers ($49.99– $99.99) to monitor your blood alcohol content (BAC). Set a reminder to take a reading 15 minutes after your last drink; the results will be transmitted to your Apple Watch, where you can compare it to past readings. The Apple Watch also features the Active ZeroLine function, which displays an estimate of when you‘ll get back to zero percent, with a countdown showing your estimated sobriety level over time.