I also carry a rescue whistle. I even keep one on my car key chain just so it will always be with me. Not as nice as this one, but effective nonetheless.
I have been laughed at and ridiculed for doing so, but I'm happy that I do.
I encourage others to think about this tool, which weighs nearly nothing (at least my plastic one does), and has a sound that can save your life by letting others know where you are.
http://www.wkyt.com/content/news/How...475875493.html