I was looking for someone to record police communicating over a radio. There were some specific things I need said so if you can help please send me a message for details. Thanks : )
There are a number of solid police scanner apps for iPhone/iPad, and I'd assume Android. Just Googling I found a database of many domains for online scanners all over the place http://www.scannermaster.com/Online_Police_Scanner_Radios_s/197.htm
What I'd do is find a station that's fairly busy (some sites/apps will tell you how many people are listening to the frequency at a given time), run a stereo cable from your headphone jack into whatever input you use for recording, and just record for a couple hours. Not sure how specific or uncommon the things you're looking for are, but I'd imagine you have all the means to this yourself.
Best of Luck, MMM