A hypervisor for server providers that does these tasks in background (without the root server owner seeing it) and alarms the provider if a hd breaks down, temperature is too high, etc! Which can then automatically react.
I think there is a need for your service, but I think it's too expensive. I wouldn't use it. A server starts at 50€ per month, why spend 1/4 of it just for monitoring?
Depends what you compare it to. If you're looking at the "free" products like Nagios etc, then of course it's more expensive. But Nagios and the like require a lot of time and effort to set up, have ongoing maintance and require their own server (no point installing on the same server you're monitoring).
It's therefore about the value the service gives you i.e. support, ease of use, fast setup, easy alerting (e-mail & SMS) and so on.