It works as described and probably I won't use firebug again for checking the headers. Some features that would be nice to have:
- instead of showing the R icon (when the target website is redirecting), show the redirection result's icon (the R can be left in a corner of that icon);
- add a "hold click" menu that would allow the following options: scan directly in HTTPS, open the redirection directly and hide/show the results in the lists of securityheaders.io;
- provide a small pop-down preview on hover.

Thanks for this, it really helps.