Rated 4 out of 5 stars
Please add fetch (http://www.freebsd.org/cgi/man.cgi?query=fetch&sektion=1) or better custom command with replacements like $URL, $COOKIES. wget is common for linux only.This review is for a previous version of the add-on (1.0).
I'm not familiar with fetch, if it supports specifying request headers and cookies then please let me know where I can find more info. Curl is already available though (it's the default in the latest version).
Edit: fetch doesn't allow specifying http request headers so it won't work. Allowing custom commands will add complexity to the UI and is really an overkill. If there's any other commandline tool that can be used, let me and and I'll add support for it.