Here's an article from Ian:
https://www-secure.symantec.com/connect/articles/building-better-collections-software-delivery
with an extract on a forum post with pretty much the same topic ^_^:
https://www-secure.symantec.com/connect/forums/report-agents-not-checking#comment-5018091
and one from me:
https://www-secure.symantec.com/connect/articles/how-check-altiris-agent-health-deploying-software-given-collection