I bought one of these multi-tool kind that has a whistle, compass, thermometer, and magnifying glass (actually caught some oak leaves on fire with the magnifiying lense) from Coghlan. It's pretty good. The whistle is ear drum busting loud, too. It's plastic, so I keep it in my small fanny pack which is always on my belt. Now I'll know just how cold it was this upcoming deer season when sitting in my climbing stand watching frost form on the toe of my boots.
They got all kinds of camping stuff over at their site, if you are interested.
http://www.coghlans.com/catalogue/index.php
http://www.geocities.com/bowhunter15...my-whistle.jpg