A robust and reliable web monitoring service
You can:

Monitor specific URLs
Be alerted by email when a web page fails to load
Be alerted by email, pager or text message when a web page fails to load after numerous concurrent failures
Include cookie information (required by some pages)
Exclude a block of time to not check (for instance, daily maintenance or backups)
Determine the frequency of checking
Determine the number of concurrent failures before emailing alert
Runs as a windows service
Logs activity