Well maybe not but it is darn close. A friend just sent me a link to FireGPG. I have been looking for something like this since I started using GPG a few months ago. It is a plugin for FireFox (Windows and Linux only so far) that allows you to “crypt, decrypt, sign or verify the signature of a text in any web page, using GPG“. Of most interest to me is that it allows emails sent from GMail to be signed. You already have to have GPG installed on your system to use it but once you do it works great.