Its quite fun to listen to live police chatter from all over the place. The app does drain the battery fairly quickly and does use data. But if you're like me, the data part shouldn't matter much. I have the 500MB data plan on Rogers and I never come close to using it all. I average just over 100MB a month and I would consider myself a heavy user. You can also monitor how much data you've used as you listen. I usually listen to it while streaming over wi-fi and when its plugged in.
Another fun aspect of this app is that you can run it while you're out and people will think you're important. Strap on a fake radio and throw in some "10-4"s and "roger that"s at key times, and you'll be an undercover cop to everyone around. I might even pick up a badge from the dollar store, tie it to a string, and put it around my neck for effect.
Check it out and let me know your adventures: http://ota.berryscanner.com/
You probably will have to configure your APN settings after installing the app to make sure it works. There are instructions at the above link.