This could be promising - but it would depend on a great number of folks participating in downloading a plugin, from what I understand. And unless you're into actively providing data by way of a download to those searching you, I doubt it is likely to fulfill its potential.
And w/the keyword tool going away soon, it also may be moot.
But so as not to be a killjoy, here's the scoop:
A free download offered by eTaktiker promises to get at that precious data falling under "not provided" in Google Analytics.
The site is encouraging any and all to download it and spread the word:
In my eyes the single goal of Google’s (not provided)-strategy is to reduce significance of (free) organic traffic and to push e-commerce companies towards AdWords. As already mentioned above, the share of ‘not provided’ traffic is increasing constantly, especially if you’re working in an online marketing environment. In our case the share is way over 50% and I know cases in which (not provided) accounts for over 80% of the organic traffic.
So, a few days ago I came up with an idea to overcome the ‘not provided’ problem:
How about creating a browser plug-in which only function is to modify outbound SERPs links from httpS://www.google.tld (secure search) to look like outlinks from http://www.google.tld? This would result in having proper keyword data of everyone using this certain plug-in. (emphasis mine)
Would love to hear from anyone who gives it a test drive!