EasyDNS offers a real-time DNS (domain name system), which allows a Web site to switch from one IP address to another within minutes. Without a service like this, a new server may not be findable by visitors for 24 to 48 hours while its IP address “propagates” gradually around the Internet.

For about $20 per year  you will be able to reroute your traffic in an emergency to your spare server that can display your emergency message or replicated server.

Very cool.