Redundant web host

I have a website that is very mission critical and my host just went down for 9 hours and was really not very helpful. I had to make 6 phone calls to get them to correct the problem and I still don't have an answer as to why it went down.

Basically I'm looking for a webhost with a redundancy package that is reputable. I have a dedicated server with my current host and what I want is constant monitoring and backup so that if something goes wrong with the server in the future the managed host would see it and switch over to a backup server and then try to fix the primary server. So I'm asking the experts. I've been trying to research this and I've found a couple of hosts that provide this but they just seem a little fly by night to me.

Does anyone know of a reputable host with these services? I don't really want the headache of managing servers which is why I want to outsource it to an expert but I do need them to take control in emergencies.

Thanks for any suggestions,

Todd