CEDAR RAPIDS, Iowa -

There's a smartphone app that can help people suspected of driving drunk. It was created by an Iowa law firm. It was designed to tell people what they can and can't do when being pulled over for suspicion of drunk driving.

"One of the biggest mistakes people make is thinking that they know their rights," said Bob Rehkemper, app co-creator.

Rehkemper is one of the creators of the smartphone application.

He says it lists basic legal rights, has a blood alcohol calculator, and an emergency "oh crap" button for when a person is being stopped.

Hit it and get advice like, "the less you say the better," "be polite," and "lawyer up."

The audio is potentially valuable evidence, if someone wants to fight a charge.

"That initial interaction is documented and is recorded so it's not a matter of what somebody remembers, or he said, she said," Rehkemper said.

But the Linn County sheriff has concerns about the app.

"It's cute, if nothing else," said Brian Gardner.

He says during traffic stops, using the program could put approaching officers on edge seeing as they might mistake a phone for a weapon.

Sheriff Gardner also worried the app could be used for the wrong reasons.

"If it stops you from being intoxicated and driving, I'm certainly in favor of it. If it tells you how to be intoxicated and drive, and get away with it, there may be some concern there," he said.

Creators estimate the app has been downloaded 4,000 times in the year it's been out.

They say they don't want users drinking and driving, but hope they'll use the app to stay informed in difficult situations.

"People end up in positions and their rights become very important to them, to their family members, to their children," Rehkemper said. "That's the purpose of this app, to understand what they do, and what they don't have to do."