Heartbeat is really your only good option other than using the built in HA, but a powered off VM is an option, but then you ahve to keep it up to date if any changes are made. That being said, Heartbeat can be a bit flaky in my opinion and we just use vmware HA for our redundancy because even Heartbeat is a short downtime while the services restart, so in essense it is the same type of failover as when a host fails.
My recommendation is to run your Vcenter servers and all component servers on an isolated VM cluster or setup DRS rules so you know where they are and rely on the vsphere HA. Heartbeat can protect from service failures, but in my experience when this happens you usually have a problem with your DB that a failover won't really resolve.