[gpm]

Do you know of a reason that this can't work with firefox, or is it probably just a matter of someone putting in the work?

[mongojunction]

I think because it's based on the DevTools protocol which is only partly supported (I think) in Moz.

Although you're right with enough work someone could engineer a way to achieve the same, even without DevTools protocol. I picked the protocol because it made it easy to achieve.

I think in future FF plans to support DevTools, or the standardised version which I think is called WebDriver protocol or something.