Would be interesting to be able to move from email or forum into chat but not requiring any chat app or remote server. Chats should also be encrypted. Can all that content live in the browser somehow, and persist across sessions? Should be able to include others as well into conversations. No one else should be able to know who I am talking to and what I am saying - well that would be a goal. Ideally no plugin required. Should be able to guarantee delivery and reading of messages.
This has a slick interface: https://news.ycombinator.com/item?id=47872083