Ross,
In theory, as long as there is a monitor on the IP:port you eventually want to load balance to, you could check the status of the node using LB::status and only send requests to a destination that is marked up. This is the default behavior for standard load balancing. I'm trying to figure out if this will work for your scenario.
What is the relationship between the hosts in the list and the servers you want to mark up/down? When you issue a redirect to one of the hosts, like mars.rent-at-acme.com, is that subsequent request going to the virtual server you're applying this rule to, or another virtual server on the BIG-IP? Is it there a default pool on that virtual server that the request is load balanced to? Is there a one to one mapping between the hosts in the list and an IP address/port that the BIG-IP is load balancing to?
Aaron