A new cellphone app produced by the State of Maryland aims to warn you if you’ve had too much to drink. Called ENDUI, as in End DUI, the app was developed under a federal grant in hopes of keeping drunk drivers off the road.

To use the app, the user informs the app of their height, weight, sex, and how many drinks they’ve consumed. Using that information, the app determines their approximate Blood Alcohol Content (BAC). The app can also provide phone numbers for local cab services or designated driver numbers that are pre-programmed by the user.

The app also has games, one of which is a reaction time tester. To test their reaction time, the user must “hit the brakes” each time a pedestrian walks into the path of the car. The game then determines how fast the user reacted and if the user was able to stop in time to avoid hitting the pedestrian.

This app can be helpful but shouldn’t be relied upon for accurate BAC information. For one thing, “one drink” may be hard to determine. Some cocktails, such as Long Island Iced Teas for example, may have three to four shots and contain the alcohol equivalent of up to four drinks. If the user counts that as one drink, the app will be getting bum information.

No one’s metabolic rate is the same and, even though the app can approximate a BAC level based on height, weight, sex, and number of drinks, the only accurate way to measure a person’s BAC is with a breathalyzer. However, it’s better than nothing and serves as a good reminder that someone who has been drinking should take a cab or call a designated driver.

The best thing for anyone who plans to drink anything at all is to have a plan to get home by some other means than by driving their own car. Even one drink can affect your driving abilities. Remember, buzzed driving is impaired driving.

The app is available now on iOS or Android.

Read more: A Cell Phone App to Curb DUIs? States Get Creative to Reduce Drunken Driving