Microsoft Knowledge Base Article 889717 contains the following summary and introduction:
This article describes how to perform an unattended Emergency Management Services installation of Windows Server 2003. Emergency Management Services is a new feature in Windows Server 2003 that makes it possible for you to perform remote management and system recovery tasks if the server is not available. This is made possible by using the standard remote administration tools and mechanisms. Emergency Management Services provides alternative access to a server if the server is not available through the standard connection methods, typically a network.