Just a quick recommendation. We were using Websitepulse as one of our extra, external monitoring systems. They consistently failed to alert us to issues (when the other systems worked). Yet, we were paying them around $80 a month. For a simple task, they should have been able to excel at the task. With all of their customers, they should have quite a margin to pay for network and infrastructure. Yet they failed.
This just goes to show… you always have overlap whenever possible when dealing with outside vendors.