+1 on the camera. You can set it on top of your pack and do Les Stroud style monologues. That might be interesting when you are an old man with kids :)
I have a Lexar MDA256-100 MP3 player than runs on one AAA battery and uses SD cards. I don't know the card size limit, but it plays well with 1GB cards. 1.8oz with battery and card and does voice and plays MP3's and is the size of a Zippo. I read on line that it is a battery eater, but if voice recording, you wouldn't have it on that long.
Another good one is the Creative MuVo TX FM. The one I have is only 256mb, but it has voice recording, FM radio, and FM recording too, as well as playing MP3's. It also runs on one AAA and is lighter sized and 1.6oz. If you can find one, they made 1GB versions too. The main module pulls out of the battery holder and has a USB connection, like a flash drive with an LCD.
There are lots of current versions, but they all use an internal rechargeable battery. I have a Sansa Clip 2GB that is tiny and light (0.9oz), does the FM/MP3 and voice trick, but runs about 5 hours max and needs a few hours for a refill. There are more modern versions that are bigger and more capacity.
Watch some brands-- they use proprietary audio formats, making editing and file management/playback a pain.