Breathometer, Inc. plans to launch what it is calling the world’s first smartphone breathalyzer at South by Southwest, an Austin, TX-based annual tech and music event, in March.

The team refers to it as Square for breathalyzers. Square is a small card-reading device that plugs into the audio port of a smartphone and allows a mobile phone to accept transactions. Breathometer works similarly with a key fob-sized device (into which you blow) that plugs into the audio port, turning the smartphone into a breathalyzer.

The thumbnail below is small but you can get a sense for how it works and the final device is said to be even smaller than the pictured prototype.

The device, approved by both the FDA and Office of Drug & Alcohol Policy & Compliance, contains an ethanol sensor, power sensor, amplifier and the aforementioned audio jack. The app will be available on both iPhone and Android devices and keeps a history of your readings. The team doesn’t mention sharing features in the audio and, for obvious reasons, it is probably wise not to build those into the app.

Whereas, current breathalyzer options available on the market (like the one we saw on New Year’s Eve) can run over $100, Breathometer will be available to the public later this year for $19.99 per unit.

Breathometer has received $2 million in funding which is being used, in part, to market the launch.

The key for Breathometer will be accuracy. In the audio recording below, Rackspace A/V tech journalist, Robert Scoble, gets a demo of the prototype but is apparently too drunk to use it properly and only blows a 0.04.