One thought is that a lot of the current/recent tools in this area focus of synchronous collaboration. And it's not clear to me that sending your collaborators a regular stream of non-maskable interrupts is the best route to great products or ideas. So how about some tools that promote asynchronous collaboration?

Not 100% sure what the next stage is, though. I personally find e-mail a pretty good medium for having a considered discussion -- but it doesn't seem to work that way for everyone. Maybe an opportunity there?