And there’s the old rule about attaching a short length of light line to a zipper pull on your pack: when it’s wet, it’s raining; when it’s stiff, it’s cold and raining; when it is sticking straight out, it’s windy; when you can’t see it, it’s dark. And so on.
Kidding aside, I carry a Brunton TruArc 3 compass now; it was what the store stocked after I gave my Silva Starter to a young Scout. Being the belt-and-suspenders type, I also have a small Brunton zipper pull compass attached to my pack, for the routine quick-check, non-precision route finding on the fly (i.e., the trail should be heading generally south), and a backup in case I lose my “real” compass. (The Silva Companion went with the Starter.)
A thermometer just quantifies pain. I used to carry those compass-and-thermometer zipper pull toys, but it was always 56 degrees. (Which meant that water froze at 56 degrees, evidently.)
In the Ohio River valley, where I hike, barometers/altimeters are meaningless. I can eyeball the elevations (“That’s a really tall tree, huh, Dave?”)