Thank you for your review.

Here are my opinions in regards with the content of your review:
1.) "Seems great but I'd imagine that a context menu option when right clicking on a url makes more sense"
Suggestion: You may use the official VT4Browser addon by VirusTotal which has that feature (context menu option) which you can install here https://addons.mozilla.org/en-US/firefox/addon/vt4browsers/
This add-on was meant to be one click in the add-on bar of the browser and it is not meant to replicate the official VT4Browser addon.

2.) "I mean if you're checking for the security of a site it makes more sense to check it before entering the actual site."
Comment: That will be a great idea that I can look forward making in the future. But I think the VirusTotal API is required for that to become a reality and this add-on was just meant for reverse-engineering purposes of the URL of VirusTotal's website. It does not use the VirusTotal API.

-TheDoggyBrad Software Labs