Website monitoring is the process of testing or tracking (monitoring) how end-users interact with a website or web application (
Wikipedia). Why is website monitoring so important for any business, any company having a web site? The main idea is: you find out that your website/web server experiences troubles of any kind, earlier than your customers.
Why is it necessary for a web hosting company to monitor its servers? Obviously, the same reason: you are notified of server downtime by a webiste monitoring service, and not by your customers. Some really good web monitoring services will not only tell you when your server is down, but also help diagnose the bottlenecks of your system. Another reason for monitoring your servers -- you'll be able to prove that "99.999% uptime" is more than just a statement.
There is one more good reason - some
website monitoring companies offer affiliate programs. You can include website monitoring in your services list and you will get a certain fee for every paying customer. Dotcom-Monitor has recently added affiliate program and now pays 25% for each customer who becomes a paid client. You can get more details on the
affiliate program here and
sign up here.