This is the tool I have been using for the last few weeks to accurately track my alcohol intake:
AlcodroidIt's only available for Android phones, as far as I know. Works with both metric and US unit systems.
The way it works is that you enter your weight and gender to begin with, and then each night you tell it what you're drinking and when you start and finish your drinks. It will count how many drinks you've had and try to estimate your current BAC in the process. I mainly use it for the former.
This app is nice because you can just enter the volume and strength of a drink and it will calculate units for you. I always had trouble trying to work out the next morning how many drinks I'd had the night before, considering very few of the things I drink contain exactly 1.0 standard units of alcohol. The app will give you a precise number -- as long as you remember to actually log the drinks! At first, it's a little bit of a hassle, but after you've used it for a week, most of the drinks you typically drink will be entered as presets, and at that point it really only takes two or three taps on the screen to log each drink.
One recommendation: If you're still drinking a lot, then after you write down the amount you had last night...clear the log. You don't want other people stumbling onto the app and scrolling back to see your drinking history and statistics on display.