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If I need to pull web pages from cron, I usually use wget or curl, which are command line tools to pull web pages.
Any competent scripter should be able to put together a shell or perl script to pull a web page and show you how to set up a cron job to call it.
On a very popular page (or all pages with a SSI), do a check to see if enough time has passed since the last report was sent. If so, then send the report. I wrote about using the CDONTS library to send mail in this [webmasterworld.com] post.
The client will want to see a mail even if they have no orders to process.
Once the site was getting regular hits I can see the method you are proposing working very effectively.