While you're at it, please add a spaced repetition learning feature à la Anki. Our brains are the best PKB, we just need the right tools to efficiently upload data to it (anki)
Every single one checked.
As for videos, I don't recall Emacs being able to play them directly, but you can easily invoke an external player.
I haven't seen any plugin to do audio recording from Emacs, but it should be easy (if you're willing to dig into elisp a bit; it's not hard) to invoke any kind of CLI tool for that, and then a/ move the output recording to a proper place, and b/ capture the link for org-mode.
> And do quick drawings with a stylus on the screen?
There are picture-mode and artist-mode in Emacs for that, but I haven't tested any of them with a stylus and a touchscreen, and draw in text mode.
How do you do the indexing part?
There are shared decks [1] and you can create your own very easily. Whenever I stumble over a new fact throughout the day, I (try to) add it to my deck. To test the system, I learned all european countries with capitals and all US states in 4 hours total (spread over weeks, just 1-2 minutes spent every other day). It's really easy and fun.
I use both the desktop and the mobile apps, they keep in sync.
I don't see any licensing or copyright terms in the list of shared decks, are those usually specified within each deck? A web search turned up this discussion, http://lesswrong.com/lw/k7a/proposal_community_curated_anki_...
I don't know about licensing/copyright of the decks.