This app is totally awesome.  Allows you to listen to over 2,200 different scanners around the world.  The scanners are provided by volunteers who stream the feed for you. The application itself is pretty basic.  When you first fire up the application here is what it looks like

Once your in select either which type of scanner you would like to listen to such as scanners near me

Or maybe the top 50 scanners

Once you have a scanner that you like then you select it and listen to it

I like to put it in the background and do other things while it's going.  What works really well is if you have a blue tooth FM transmitter in your vehicle then let it play through your speakers in your car/truck while your out and about. 

Use this with your bar code scanner to install the app directly on your phone.