Enhanced Monitoring for Amazon RDS allows you to net deeper visibility into the health of your Amazon RDS instances in real time. It provides a comprehensive set of over 50 new system metrics and aggregated process information for your instances,at granularity of up to 1 moment. You can visualize the metrics on the RDS console, and also integrate them with CloudWatch and third-party applications. Enhanced Monitoring for Amazon RDS was earlier made available for MySQL 5.6, and now it is also available for MySQL 5.5.
Source: amazon.com