Nice work. I think I might have found a bug: Scalling the brush on the white board doesn't seem to work. (on my keyboard that would be alt+8 and alt+9).

What does "1v1 chat" mean in the readme, characterizing services like hangouts?

Pretty much, most other services for chat are for single participants like hangouts (or most XMPP clients) and it doesn't make it particularly easy or obvious how you would invite others. That's generally what I meant by 1v1 when I wrote that.

Right now, echoplexus will broadcast to everybody in the channel (unless you whisper). In the future, we'd like to use WebRTC data channels for pure P2P 1v1 chat (possibly also allowing GPG for identification and encryption) falling back to the whisper-like implementation if unavailable (but trying at all times to make it clear how you're connected)