Startup Idea : Intoxicated or not?

Hi Guys, I had this idea about an app that tells you whether you are intoxicated or not and would appreciate all inputs. I don't mean the existing apps out there which require inputs such as age, wt, drinks... This idea is based on a person's reflexes. For eg - A target moves across the screen on your phone in a random manner and you are supposed to hit the target in a given amount of time.The first step would be having a reference performance point. Store your performance on this test without any alcohol in your system i.e hit rate, misses etc and it would serve as a reference point. After a couple of drinks retake the test and based on your reference performance on the test, the app would tell you whether you are intoxicated or not. Worse the results, the more intoxicated you are. The results would determine your level of intoxication.The new (not mature yet) eye tracking technology could also be used. The app would have a target move across the screen and based on the initial calibration of your eye ( without any alcohol in your system)and the your tracking performance ( with alcohol in your system) , the app can judge the alcohol level.