You are correct that it is much easier in Essentials 2010 (which is now available) to create a ping monitor - there is a wizard in the Authoring workspace that will help you quickly create them.
For Essentials 2007, have a look at the following blog postings for guidance:
http://contoso.se/blog/?p=189
http://www.snowland.se/2007/10/23/scom-script-to-ping-one-ip/
Thanks
Richard
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