1. 5-0 Radio Police Scanner
5-0 Radio Police Scanner is one of the most popular downloads in the App Store. It's been in the top 100 most downloaded apps since 2009 and has more than 20 million users.
That's because it's loaded with emergency and ham radio feeds from around the world. You can browse by country, state or city, and save or share your favorites. This app includes a handy reference guide for police, EMS, fire and military codes.
You can also listen to these feeds no matter what gadget you are on. If you want to listen on your computer, or on your smartphone or tablet while running other apps, all you need to do is email yourself a link and voila!
This app is free and is available for Apple smartphones.