Sequoia is the code name of a project recently started to combine Twitter microblogging with group conferencing and IM features, based on the GroupChat Server / Jabber architecture.
1. A Twitter account is associated with a GroupChat, multi-user-chat room.
2. All @replies to this Twitter account will be ReTweeted to to the account timeline - e.g. replies send to Twitter account "sequoia" will be displayed at twitter.com/sequoia timeline with format "[ @fromuser ] my message". Thus, this account itself acts as a room in Twitter which can be followed. Followers automatically get the friendship status.
3. Furthermore @replies are also send to the associated GroupChat room. Each message in this Jabber chatroom gets forwarded/tweeted to the Twitter account too.
A screenshot is showing this conversation in action:

Some playground: This chatroom was bound to this Twitter account to try things out.
GroupChat Server on the one hand is the Jabber backend, powering multi user chatrooms, on the other hand it enables Twitter group conferencing by processing @replies and acting as a gateway between the Jabber and the Twitter world for message exchange.
The prototype at this moment is a mix of realtime (Jabber) and near realtime (Twitter) communication ways. A mix of feature rich text, audio and video conversation possibilities with the strength of social networking.