Yapta API

Yapta aims to help travelers get a better handle on pricing by providing easy-to-use tools and information that assures they get the best value from their travel spending.

The APIs enable applications to track pricing on specific flights offered from hundreds of airlines around the world. Flight prices can be monitored both before purchase -- in an effort to help travelers buy at the lowest price -- and after purchase, in an effort to help travelers capture an airline refund when the price drops."