Lidenbrock is an add-on to Core Data. It is a solution to easily synchronize your Core Data models with some external JSON resources.
This project was made as effort to build a link between CoreData and external data storage. However it lacks of a lot of key features (like an HTTP client). I realize how far this project is from some existing great libraries. Unfortunately, I have not enough time to work on it seriously and won't update it anymore.
If you come to this page looking for a solution to build your connected applications, I suggest you try the great RestKit library.