Gives you a popup where you can choose the value for a given HTTP Header. You can define domains on which this should be happen, the name of the HTTP header and a set of values to choose from in the Firefox addon options.
There was this authentication reverse proxy in front of my web application that set an HTTP header to a username. My app authenticates the request based on this header value only. For development my browser set this extra header. I need to quickly switch between a set of accounts. No existing plugin got this done with less than 5 mouse clicks.
I know, it was done to work, not to be stylish. Send a pull request!
It's build using Firefox's simple-prefs API. As this API is limited and i'm way to lazy to build a gui to define a dynamic number of options: Send a pull request!