Seems like a pretty good idea to me.
The only issue I can think of is what the other dude was talking about.
Who is liable if the machine fails and someone goes out drinking and driving or potentially kills someone?
A beathilizer really has limited impact on the decisions drunk drivers make. Whether you're at .08, .11, or .02 99% of the time you have your mind made up before you even start drinking if your driving home or not. A breathilizer may give you peace of mind or the people your with peace of mind; but anyone who puts their life in the hands of a cheap little gadget with the intent to blame the test if it's .02 off and you ended up with with a dui at .09 needs to load up a bowl, sit down for a coupe hours, and really analyze their life. Beathilizers are tools created to confirm your drunk after you already are not to help you determine how many more your body can take before getting behind the wheel.