in reply to
How do I tell if a remote site is up?
You haven't actually stated what will happen (or what you want to have happen) if the remote site is actually 'down'.
If you want notification by eMail (and lots of other diagnostic tools) then try Nagios formerly known as NetSaint. I recommended this before a few days ago and is a very good solution for this type of scenario.
From the Nagios site:
What is Nagios? An open source host, service and network monitoring program. Who uses it? Lots of people, including many big name companies and organizations.
It's also written in perl... HTH