The HA xVM agent is available for download in the Open HA Cluster community! You can find the details at: http://opensolaris.org/os/project/ha-xvm/.
To get you started quickly on the topic, a cheat sheet has also been provided! Now that is what I call user friendly! 
The design document has been updated to include the latest feedback as well.
This is an important milestone for the project. Happy Clustering!