Coghlan's Four Function Whistle

Not too bad of a small tool.

I keep this lil deal clipped to a strap on my pack just for a quick glance to get my heading. I would never use it for my primary compass though. Most water floaters are not to be trusted. 

The temp gauge isn't too bad, as long as you don't keep it in your pocket. It comes with a fairly loud lil rape whistle, lucky I haven't had to use it yet. LOL.