Rated 4 out of 5 stars
Hello! I think this tool has great potential. Here are a few of my suggestions (please bear with me:):
1. The CS lite addon has a few great ideas (https://addons.mozilla.org/en-US/firefox/addon/5207). For example, a single click will bring in a host of options (Allow cookies globally, block, remove etc...). You could do the same thing here.
2. You could also have this tool block/allow all referrers globally (have a global setting) and then have the user set personal preferences for each site. Again this is a CSlite setting!
It should also block referrers from other sites as someone already mentioned before.
3. last but not least, please change the icon! This is of course only my personal opinion:).