I constantly monitor online, local police, fire, ems, rescue helicopter, etc., on :Broabcastify": http://www.broadcastify.com/listen/
Normally, Chicago is the top feed, but currently, Boston is the top feed, at 2754 listeners.
With this online monitor, you can listen to countless types of feeds, world wide. I listened to floods in Australia a few years ago. I also heard one hell of a chase some months ago, right here at home. You can also listen to trains, even Amtrak and Amtrak police. You can also find some CB feeds. There is a major marathon coming up in ther UK soon, and I definitely want to hear some of that. You can listen all over the world, but if you don't understand the language, it's no fun.