Good idea, but can't use it Rated 4 out of 5 stars
This is a good idea, however it's not usable if one has hundreds if not thousands stored login information/passwords.
All I see is a orange square with some tiny white dots and green and blue odd shaped "dots". These colored dots move at about once in 5-10 seconds. While the addon is active the browser is unusable. Perhaps async execution is in order here...
@Laurentj: It does require master password, but if you did not know that, once you entered your master password it will be remembered by Firefox until you close it, therefore anything that requires access to MP protected data will have unrestricted access. This is not addon's security issue, it's Firefox's itself! There are some extensions that would timeout MP after specified time.