I carry a couple, a cheap one with a thin single note for teaching archery (I run my line with a whistle) and also carry a fox-40 on the ribz-pack-o-doom for the unlikely need of a SAR type situation, and the more likely need of absolutely getting the attention of a bunch of kids. I can make myself heard with just my voice, but it tends to trash me for a few days afterwords. Also, I like to keep well ahead of Mr. Murphy. As far as normal urban wanderings, no, but I can see if I did any park walking or similar it would be worth while, any place where you might need to call out for help, you should have a whistle, they beat a voice by a long way, and its unusual enough that you can break into people's zoned out-ness.