When I was a kid, my uncle had an old CB radio in his kitchen, and some nights we'd sit around listening to the police and fire bands, just to "see what was going on" around town. It was a strange feeling, spying on these crackly voices of authority coming from who-knew-where, as they reported on trouble in all its varied forms in a dependable, businesslike monotone.
That was the 80s, but apparently, there are lots of people who still enjoy listening in on police frequencies -- so many, in fact, that one of the more popular mobile apps of late is 5-0 Radio, which allows you to tune into police scanners from major cities all over the world. (London? New York? Paris? How cosmopolitan!) One caveat: I had an embarrassing experience with this app, accidentally clicking on it just before I went into a meeting. Suddenly my phone turned into a squawking police radio, and due to some glitch, neither quitting the app or even muting my phone would shut it up! It was like that scene in Spinal Tap ... you know the one I'm talking about.
Anyway, the police scanner thing has gotten so popular that now it's entered phase II of virality: the mashup. Introducing YouAreListeningTo ... which mixes the police scanner of your choice (here's Los Angeles) with ambient chill-out music, the combination of which is kind of profound, in a 90s-era-rave sort of way. So snap a glow stick, make yourself a cocktail, and give it a listen.