VoodooPad is a sort of wiki for your (OSX) desktop. You can put in text, images, and sketch things out. I assume if you have a writing tablet you’d be able to use that instead of the mouse pointer to draw, and perhaps even to write out notes to yourself and let inkwell convert them to text… not sure though, I don’t have one. :-)
Free 15 page trial, but you’ll have to shell out $25 to get the real thing. It supports encryption, also, so your jotted down instructions for the doomsday device will be safe from those meddling kids and that darn dog. Just be sure to follow the advice on the Evil Overlord list and set your password to something the average 6 year old cannot crack on his first try.
You might like Instiki, which is works really well on OS X. It runs in the browser so you don’t get WYSIWYG editing, but it’s free and very polished.
Uh, hello? Find me one techno geek that would prefer to jot notes with their hand parked in front of their desktop when such laborious tasks can be accomplished with the expedience of a modern ergo keyboard?
Until the day arrives that portable tablets drop from the $2000 range to the $200 range and this software can be successfully ported, do I see it having any appeal in practical application whatsoever.