hmm, I was going to experiment on this hackernews page, so I clicked on Extensions->BrowserFlow and it opened a window with a single button "Sign In". So it appears it does not work locally at all.
Question: Is there a technical reason for this, or you just want to insist that everyone create an account for some reason?
I do not see an obvious reason why macro recording and playback could not be performed purely locally. So I am skeptical that a server is needed, but always willing to learn and be astonished...
I would think that even if (big if) a server is needed, it could be done anonymously without need to collect email and create an account.
Anyway I am uninstalling the extension until such time as there is a local-only mode. too bad, from the demo it seems neat.