You might if you've tracked your drink intake with Buzz Buddy for iPhone and iPod Touch ($0.99). It can't guarantee you'd pass a breathalyzer test, but this blood alcohol calculator gets close.
After entering your gender, weight, and whether you've already consumed alcohol, you'll tap the drink type you're about to imbibe--standard measures of beer, wine, cocktail, and shots. That means if you're sipping a strong Belgian ale or Long Island iced tea, you had better 'fess up.
Using your weight and gender, Buzz Buddy will graph your calculated blood alcohol level over the hours, helping you predict when your levels will get back into the safety range. If you spill over from sassy to sloppy, the colored indicator will supposedly shift from green to yellow to red and you'll be warned that your blood alcohol level is far too high to drive. A small bug in version 1.0 kept the indicator green even as we "chugged" enough booze to fell a mule.
We have some other ideas for expanding Buzz Buddy's possibilities. What about calling an emergency contact from within the app? Or viewing an in-app map detailing late-night munching spots nearby? Entering submissions to the graph retroactively, to account for the drinks you may have forgotten to add as you got swept into your evening, however, is a more urgent request.
With a button you can tap to call a cab and arguably helpful tips to instill a sensibility for responsible drinking, Buzz Buddy is a good idea--as long as you have the the presence of mind to use it.