goodintentions mentions 2 stylus brands perhaps one of these might suit your purpose (I'm looking for one too)
He writes " I take notes directly into these pdf books with a adonit job stylus and a dagi stylus. Right now, these are the best styli on the market for capacitive touch screens"
Might be worth asking him for his experiences/input...
Just google Adonit Jot and Dagi P601 or P602. Either one of these is extremely accurate. There are many note-taking apps out there, but the best one I've found are repligo and ezpdf, either of which you can hand write directly into the pdf document. I would imagine this is particularly useful when you are provided by pdf notes from your professors and you can just add in your own notes on top of the pdf's.