Ways for a phone to tell if you are drunk?

Hey guys.. I am creating a phone application and I am wondering if their is any proven ways for a phone to (somewhat) accurately decide if a person is sober or drunk?? I currently am using a computer generated math problem such as 6*5-3+5 that the user must answer to tell if he's sober.. Any other suggestions would be great.. Also, keep in mind I have access to the accelerometer (which I do not suggest using).. Maybe memory game??