I'd also be curious to hear what you're doing behind the scenes. Also, what's the general method for extraction the primary content of a page the way you do for the lightbox preview?
Overall, it's very fast and the results seem relevant, plus you've identified a niche where you can get a foothold, so I think you're on the right track :)
We want to make the search widget customizable and in general unobtrusive, so it should fit well on any site. Initially we target blogs mostly.
Behind the scenes we crawl the websites with our own crawler, we filter the content and run our own algorithms for building and ranking expressions.
For the preview we use TopUp (lightbox clone) and we filter the page with arc90's readability algorithm. If someone is interested we can write a blog post with more details about the tools and libraries used.
For monetization, freemium would be the default route. What would you suggest otherwise?