Hmmm let’s apply some real constitutional law to the subject. 2ndLaw, shame on not being more complete.
When an officer pulls you over for suspected violation of the law, he is entitled to do certain things. He is entitled to ask for your license and registration. He is entitled, having pulled you over, to look inside your car from the outside and see what can be seen. He is not entitled without further evidence, unless you give him permission, to search the interior of your car or the trunk thereof.
The device in question samples the ambient air inside the car near your head, in an attempt to determine if your exhaled breath contains detectable amounts of alchohol. This is, of course, a ‘search’. The question is, is it akin to the limited search of inspecting the interior of the car from outside the car to see what is in ‘plain view’, or is it more akin to the sort of search that requires probable cause to conduct, such as opening the trunk of the car?
One could argue that all the device is doing is the same thing the officer does when he smells your breath. Clearly, if I open the window of my car, and the officer detects the odor of alchohol, I’m on my way to further investigation of whether I have violated the law. This is nothing more than a nose with a better sense of smell.
On the other hand, we now have an attempt to reach inside the car, drag out something from within (the air the device takes in) and subject that to analysis. That sounds pretty intrusive. If I refuse to open the window of the car, the officer isn’t entitled to break the window to sample the air inside; that would be a violation of the Fourth Amendment (or the Fourteenth, if it is a state officer, as it likely is). So which do we have here?
At a guess, the police will use the device, the defense attorneys will move to dismiss the charges, the courts will slowly build up decisions one way or the other, and, eventually, the Supreme Court of the United States will be required to advise whether such an action is or is not a violation of your rights under the Constitution.