The Pingdom service monitors websites and servers from multiple locations on the Internet, making sure that they are working. You can use Pingdom to monitor both your public and password-protected websites, your FTP servers, your email servers, and any other kind of service that should be accessible from the Internet.
If your site stops working, Pingdom will alert you immediately. Like a watchdog.

Pingdom keeps reports of all errors it detects, and these reports are always available to you online via the Pingdom control panel. You will be able to see when the error/downtime happened, how long it lasted, what kind of error triggered it, and for each outage Pingdom also performs an additional error analysis.
Depending on the kind of error, this extra error analysis includes several steps, including checking that DNS lookups work, traceroutes to locate network problems, saving of the actual HTML page at the time of the error, the header response from the server, and so on. All of it to help you find out what went wrong.
Pingdom has reports that track the performance of your sites and servers through the lifetime of your Pingdom account. They allow you to see various trends in downtime, response time and load time.
In addition to the graphs and detailed reports in the control panel, Pingdom can also email you daily, weekly and monthly reports on the uptime and response time of the sites and servers you are monitoring.
It is also possible to enable a public report page that can be viewed by anyone on the Internet, where a selected set of what you monitor shows up.
You can easily configure Pingdom to inform you and your staff via email or SMS as soon as we detect a problem with your sites or servers. Since Pingdom tests your site as often as every minute you can be quickly informed of any problems.
“After several months as a subscriber to the service, I can recommend it.”
Review by Ben Gross