If you need your cellphone to decide if you’ve had one too many, that’s probably a sign you should call a cab or car service. Nevertheless, the state of Maryland has just launched an app (funded by the federal National Highway Traffic Safety Administration), that will tell you your approximate blood alcohol content (BAC), test your reflexes and even help get you home safely. If you’re a 130-pound woman who had a glass of wine, for instance, it’ll show about a .04 BAC — one drink below the limit, and already an unsafe level for the road. It’ll also test your reaction time with memory games and a simulator that makes you brake for pedestrians. When the app determines you’ve had too many (or any, for that matter), it’ll get you the number for a cab or preset designated driver. An official said the goal is to take the “brainwork” out of drinking and add some common sense to situations where none may exist.