Since they are probably trying to do the same thing as the firefox and other browsers ‘do not track’ option which is a request, which sites can choose to comply or not, I don’t really know if they are worth anything more.

The other thing, tracking would be cookie or script based, so something like cookiemonster for firefox would put a crimp in any cookie tracking plus if you don’t accept 3rd party cookies in your browser settings, tracking is going to be a bit more difficult. Then there is NoScript if said tracking were script based and also RequestPolicy add-on which blocks cross site scripting.

These would up to a point make these add-ons pretty redundant.