It's usually easy enough to add the site, by simply writing its name, but it could be easier.
I'm thinking right now this:
- Compile a browser without the cross origin limitations
- Make a site that uses iframes with all the answer-providing websites in it
- Simply focus the text input in the site/iframe you want and search away
- Have a way to open the results in your main browser or just use that patched browser
Like one of those internet explorer toolbars, except they cover the whole area.