Ask HN: Would you use a review sentiment search engine? 12 years ago
I agree with @manmeet that the algorithm for the sentiment analysis has to be great; the search algorithm also has to be tremendous to convince me to switch from Google or DuckDuckGo. To avoid the challenge of making a new search engine, maybe you could build a plugin?
Somewhat similar sentiment analysis, for terms rather than unique entities: http://www.whatdoestheinternetthink.net