This is probably a case of "if I new what it was called, I could google it in 5 minutes" - but I don't know what it's called.

It's probably best to explain the requirement using an example. We have a number of services (vpn, owa, etc) which we host from one of our datacenters. We have a number of datacenters, and we technically have the infrastructure already in place to support these services at a number of our datacenters. To provide access to these "services", I would create an external DNS entry (ex. VPN.MyCompany.com > Gateway IP for one of my DCs), and clients will connect to it via the DNS entry. Since I have multiple datacenters that can support this service, I could theoretically offer a "highly available, geographically dispersed" solution if I could point this DNS entry to some sort of third party who offers highly available "redirection" services. If my primary site goes down, I could just make a change via some management console and configure the redirector to point to a different DC. Of course, it would be fairly straightforward to set this sort of thing up on one of our servers, but that would kinda defeat the purpose of a highly available third party.

Is anyone familiar with a service like this? I'm thinking something like DynDNS, but with Enterprise availability guarantees.