The State and Notification Broker provides APIs that allow developers to monitor over 100 system states from managed code, react to changes in those states, and create custom states. It provides a consistent model for accessing and managing system states without using P/Invoke. Developers can read states like battery level and be notified of changes to react to in their applications, such as disabling buttons when battery is low. The broker also allows applications to launch when a monitored state changes.