SiteUpTime.com

Sometimes your website goes down and you realize this fact only after a visitor, friend, colleague, etc. notifies you. Now you can have one website monitored 24/7 fr*ee of charge with the SiteUpTime.com service.

Multiple monitoring servers around the world run protocol based tests on your website at specific intervals (every 2, 5, 15, 30 or 60 minutes) 24 hours per day, 7 days per week, 365 days per year to insure that your customers and users can reach your website. If more than one location detects a connection failure, an email or SMS alert is sent to you.
Their software tracks these failures and logs in detailed reports of the uptime/downtime of your website each month. These reports are available to you to browse via an account control panel. You can monitor additional sites for as little as $5/month.

Begin monitoring your site here.