I've been playing around with getUserMedia today (via RecorderJS), and in Chrome, it will display a pulsating red button over the favicon whenever it is streaming the data. Pretty neat.

I'm still going to do a lot of messaging around the recording state in the page itself, though, because, I'm not actually recording the whole time that the media stream is connected - I just have it connected the whole time so that I don't need to re-request permission to record.