The DrinkShield is an open source Breathalyzer kit for the Arduino. It’s a great starter kit that was originally designed for Hackerspace parties. The DrinkShield can work as a standalone breathalyzer or you can connect it to a computer for and interact directly with the results. Source code repository comes with a game to use as a proof-of-concept.
Hot Topics:
I think it’d be cool to integrate this with a lockbox which won’t open unless you blow a < legal limit. Great to keep your keys, phone (no drunk dials), or the power cord/battery to your computer (no drunk emails/facebooks). Just make it so the lock isn’t easy to defeat using brute drunk strength.