I posted that link a few months ago and it was pretty well-received. Today's submission is more iterating -- the one in the link offers a basic frame-only interface but today's submission is a full network stack

I considered the cross-tab case but couldn't think of an obvious way to implement that. They'd have to get mic permissions, at any rate

Oops, I guess I forgot I approved the mic on that domain already. That's a fair point and it would keep user privacy intact. Excellent demonstrations either way. It's like an audio QR code. Very inspiring!