BEST

I keep getting an error that Firefox is blocking cookies and it's only blocking third party. If I navigate to hangouts.google.com and have no problem signing in.

This may be a very useful add-on, but it gives me no way of choosing which Google account I want to use or knowing which Google account is being used. Add that capability and I'll try it again. Without that it is useless to me.

Your add on is great but can you add some feature that notify users when someone chat to them ?

A pinned tab + setting ctrl-tab to visit tabs in most recent order is pretty much superior - this addon's pop-out widget just displays the hangouts page, but it reloads every time you open it, so a very nice delay there. It also asks for the "read all webpage data" permission for some reason.

Unfortunately that seems to be what all these hangouts plugins do...

Maybe add some way to quickly respond to messages when you get one, like the respond-in-the-notification thing that Android apps tend to have? This would be somewhat complicated I imagine, but it would make for a killer extension.