Otherwise, set up a couple stable IPs to redirect to a subdomain and nothing else. (I'm comfortable putting two quality machines in different data centers for this, but you can use a load balancer it you have access to quality load balancer). If all of your published urls have www (or m) and all of your inbound links have it too, it's not really a big deal if the root domain is unreachable for some time in the event of a server/load balancer/datacenter failure.