Implementing a JSON comparator to check whether the given two JSON strings match each other and if not where the difference is. This can be developed as an online tool using JavaScript/ jQuery or a standalone application using java.

Useful links :

http://en.wikipedia.org/wiki/JSON
http://www.json.org/js.html
http://www.developer.com/lang/jscript/top-7-open-source-json-binding-providers-available-today.html
http://www.tutorialspoint.com/json/json_java_example.htm