What does the service monitor?

Some services monitor only whether your site is up or down while others produce much more elaborate information about a user's experience. It doesn't take much effort for a service to ping your site several times an hour to determine if it is up, but that doesn't tell you much about how your customer perceives you. If your concern is your customer's experience, that should also be the site monitoring service's concern. That means it should offer accurate information on which elements of your site perform well and which perform poorly.

Aside from sending alerts when your site goes down, most services will give you information about response time. The next feature you'll likely want is some data on download times. These two terms are often defined a little differently: Response time will almost always be the time it takes for the initial part of a page download (DNS look-up, TCP/IP handshaking), whereas download time includes information on the download of the components that make up your page (images, applets, etc.).

Are the alerts and reports accurate and relevant?

Efficient reporting is essential. You don't want to be digging through endless screens to get to the data you need, and you don't want to be limited to a canned reporting structure that you can't use. Most services have some sort of free trial, whether real-time or otherwise try them out. When evaluating the data, it's important to keep in mind how you will use it. It may be impressive to receive lots of data, but is it useful? Is it really the data you need?

Does the service provide enough information to resolve problems?

As with reporting, it's not the amount of data you receive that matters but how you can use it. Remember to keep your objectives in mind: Do you need to know how your site appears to customers, or do you simply need to be alerted as to whether your site is up or down? Being told that the Sprint backbone in the Southeast is slow may not give you the information you need when it's your own site that is slow to load in general.

How responsive is customer service?

Last but not least, how helpful will a site monitoring service be when you run into a problem or question? Will a bargain-basement service be of any value if it doesn't offer you technical support?

Choosing a site monitoring service depends first and foremost on what your objective is, whether it be confirming uptime or downtime, or measuring your customers' experience. It may seem like enough to just monitor uptime and downtime, but don't underestimate the growing importance of customer experience. With as much competition as there is on the Web, you need to find the right site monitoring service: one that can, and should, help you make the most of your customers' time on your site.