A unified mechanism for storing device, application, and service state, as well as a rich notification brokerage architecture includes a notification broker. Clients register with the notification broker to receive notifications for changes to state properties. When a registered state property changes, a notification broker determines which clients to notify of the state change and provides the client with a notification regarding the change. Clients may be notified whenever a state changes, when a state change meets a predetermined condition, or based on a schedule. An application may also be launched in response to a state change. An application programming interface (API) is provided that provides a unified way of accessing state change information across different components within the device.