I wrote this over the course of 2 nights, about a year apart! It's mostly an experiment with knockoutjs and local storage. Feedback, issues, or pull requests are welcome. I am sure there is much room for improvement :) I turned off user defined key entry for now. URL detection seems a little janky, but regexes are not my strong suit. Learned a few things along the way, like IE does not support local storage when run from a file system. Thanks!
In case you didn't know, this is a pressing concern for developers that do care about performance of responsive websites. Take a look at http://www.w3.org/community/respimg/
Scott Jehl of Filament Group just delivered a talk at An Event Apart on Responsible Responsive Design, and released Southstreet, a suite of tools designed to make responsive design more performant. Check it out at https://github.com/filamentgroup/Southstreet
By the way, if you scroll ALL the way down to the bottom of any question page you do see the best answer. Apparently they bank on the fact most people won't scroll that far and get discouraged by the "paywall" on the top. The Google crawler requires the text to be visible I've heard