Sending alerts to various different groups

HI,

I have some servers which are deemed critical and others which are deemed not so critical.

Both the critical and non-critical servers can be pretty much anything, SQL, AD,  IIS, app specific.

I was thinking of tagging the critical servers in the registry.

Then my goal is to add a key word, e.g: "Critical server" in one of the custom field of the alerts.

But how can I do this for all possible monitor(s) and rules which exists in my environment?

thanks