You don't have to take our word for it that breathalyzer apps are useless. Just ask John Elder, public information officer for Minneapolis Police Department.

"It's a great gag if you believe in magic," he said.

They're worse than just being worthless. "The apps are providing improper information, that's not better than nothing," he said.

"The instruments we use to determine alcohol concentration are highly sophisticated instruments checked and calibrated with routine regularity, and it goes through a series of internal and external calibrations to ensure that it's accurate."

OK, but how about the breathalyzers found in bars?

"So many things that come into play: the ways your body metabolizes alcohol, your fat content, lean muscle content, how stressed you are, if you're tired, if you're really tired," he said. "These don't take any of this into account."

Bottom line: The only test that really counts is the one administered by people driving the cars with the flashing red lights.