I'll give it a try. Just so I'm clear, I checked their site and it appears that it creates a cluster. In a simple passive/active case, the heartbeat software monitors the services I choose to, in this case apache, and in the event it is unhappy with the results of the test, it shuts down apache, and then releases the ip on the first server and gives it to the backup serverso the router never notices a difference and then starts the backups apache. So I presume originally you set the backup server another IP and if the switch occurs, the IP will be changed and the first presumed dead.
Also can you have it run additional scripts when it does the switch, say an email script to let me know the switch occured