Scanner Radio is an Android app that lets you listen to live police radio, fire radio, and weather radio as well as amateur radio streams from around the world. There are over 2,000 channels available.

The app grabs the internet streams for these police scanners and other radio channels, so there may be a slight delay. But you can click the “Scanners near me” button from the home screen to find local streams. Or you can choose the top 50 scanners. It turns out that the Chicaco Police radio stream is one of the most popular, and for good reason. There’s a lot more chatter on that station than the Philadelphia scanners I tried at first.
For the most part, I find listening to police radio to be as much fun as watching paint dry, but if you tune in long enough you might find some real drama unfolding in real-time, or get some information that can help you avoid an accident on your evening commute.
Scanner Radio is available as a free download from the Android Market. There’s also an ad-free Pro version available.
via reddit
WARNING in many states if you are not a police officer or a hold a ham radio license you may be breaking the law if you use this in the car.
In face just the other day was a news story about someone who got cited by a cop after being pulled over and just having one of these apps installed on their phone.