It's just a demo right now, but Ryo Shimizu's ZeptoPad 2.0 whiteboard app looks pretty promising. We already love collaborative drawing apps like Netsketch, but Ryo's whiteboard adds a couple of interesting tweaks—the ability to watch the whiteboard live via a web interface or on what looks like a local client, and then save everything to PDF when you're finished. If collaborators are not limited to being on the same wi-fi network, which is how these apps often work, sign us up. Barring any Apple hold-ups (that's never happened, right?), ZeptoPad should hit the store next weekend. [Thanks, Ryo!]