"- The compass is probably less than an ounce actually, has a thermometer which is good just so I can get some satisfaction out of knowing how bloody cold it got the night before, and I have heard that a compass is good on the AT just to make sure you are walking on the right direction if you go off trail and return."
I have a small clip-on watch band compass attached to the end of my sternum strap. It's nothing I'd want to depend on for cross country navigation, but really all that's needed for making sure I'm headed the right direction on a trail. Here's what I got from Amazon:
I check them against my Suunto before attaching to the sternum strap to make sure they point to north correctly (no declination adjustment, so you have to keep that in mind). Just to make sure they don't fall off, I put a drop of super glue on the closure.
You can either purchase on from Amazon or your favorite gear store, or PM me your address and I'll send you one. On the AT, it should be all the compass you need.