This extension seamlessly adds the ratings from IMDb and Rotten Tomatoes into the Prime Instant Video web interface. Each movie and series detail page gets two more rating entries (if the movie/series can be found in IMDb).
The ratings for Prime Instant Video extension uses the Open Movie Database API by Brian Fritz (http://www.omdbapi.com/) for querying IMDb and Rotten Tomatoes. Thanks Brian!
The source code of this extension has been released under the MIT license - feel free to collaborate on enhancements and improvements here: https://github.com/joscha/prime-ratings
Neither this extension, nor its author is in any way affiliated with amazon.