Using DNS Failover allows you to redirect traffic to a backup or alternate site when your primary site is down and if you are a user of the giant Cloud provider Amazon, you can run your primary application simultaneously in multiple regions around the world and fail over across regions. With DNS Failover, Route 53 can detect an outage of your website and redirect your end users to alternate or backup locations that you specify.
Read more here – http://aws.typepad.com/aws/2013/05/amazon-route-53-elb-integration-dns-failover.html