How to know if 'mysql index' are used or not in all database or table?

I read similar topics without success :/ I'd like to know how can i determine which index are used in my database or table :

DATABASE Is there any tools, or SQL to use on the database, which can give me information about index used or not ? I'll prefer using SQL but if a simple and free tool exist i'm interested.

TABLE About the table and index used on it, the only way would be to determine all queries which use that table and to do an EXPLAIN on each in order to determine if an index is used or not ? However it's meticulous and complex to gather all queries of my app and to make an EXPLAIN so i'd prefer having a tool, sql or anything else which could tell me index used or not in a database

Any ideas ? Thanks William