BACtrack Mobile Breathalyzer lets you accurately measure how much alcohol is in your system and send the results to your iPhone/iPad. The application will be able to estimate (in time) when you are sober enough to talk with others. Also the app can take notes and pictures of your drink and can keep them in a drinking diary (and share them on Facebook and twitter).
Who the hell want that? Is the perfect evidence for your girlfriend/wife to know what you did last night and how much did you drink. "No darling, I'm not drunk, I had only 3 beers !"
The BACtrack Mobile Breathalyzer had an internal air pump which and very good sensors which insures very precise results. The diary is capable to be very personal