Monitor your Website’s Uptime with Google Docs

Here is a great GDocs script that will email you when your site goes down/up.

http://www.labnol.org/internet/website-uptime-monitor/21060/

Follow the instructions in the author's page and you will end up with your own copy of the script.
If you want to email multiple recipients instead of just the one, here are the changes I made to support that:

from line 47 onwards:

ScriptProperties.setProperty("status", code);

var recipients = email.split(";");
for (r in recipients) {
if (recipients[r] != "") {
MailApp.sendEmail(recipients[r], msg, error);
}
}
// end of code changes
Many thanks to the author +Amit Agarwal

ps: Comments and/or links to this article are most welcome!