Ask HN: Brainstorming project ideas around Bitcoins. Any ideas?

I'm looking for a side project and Bitcoins have piqued my interest lately. One initial thought was a web app that provides (semi) real-time stats on BTC price velocity and possibly some predictions based on historical behavior and such. Another is some sort of command-line tool for interacting with bitcoins or facilitating transactions.

Just looking for some more ideas. I'm open to pretty much anything as far as language and app. The more likely it is to actually be useful to people, the better.

Thanks in advance!