I wrote a field notes application for my pocketpc a couple of years ago. Besides all the normal things, it even had the ability to let you do a small sketch of the subject. I got it to the point where I could field test it and I have to say that, while it is a great idea, it is IMO a flop in actual use. The LCD screen isn't really bright enough to see well out in the sun, you have to carry yet another piece of gear with extra batteries, etc, and then figure out where to stow it amongst all of your other gear. After several weeks of pretty intense use, I chalked it up to a great idea but not all that practical. I reverted to the 3x5 notecards that I've been using for the past 25 years. They are smaller, faster, cheaper and I can stick them in the plastic bag with the holder.
That's my 2 cents....
Allen