http://lifehacker.com/deeper-history-searches-the-contents-o...
http://www.hongkiat.com/blog/chrome-deeper-history/
That being said, there are serious security concerns with kind of project (which is why I stopped development) and likely why full text search was taken out of Chrome by google years ago. It is not insurmountable, by any means, but I didn't like the idea of know that if I was successful and reached a very large audience that I might also be responsible for serious identify theft and other hacks.
I'll also point out that I did collect usage stats for a time, and they were horrific. At my peak I had ~5000 installs and out of those 5k something like 3-5 searches/day was the norm.
I would be happy to share my experience with the dev team. I still have code that may be of use as well.