See also the admin/monitoring page.
We differentiate between two types of monitoring:
System(low level) based monitoring (e.g. by a nagios agent) running on the server which monitors the CPU, RAM, and other health sensors.
Application(high level) based monitoring for which we have added a monitoring page. Our currently available application sensors are described there.
Depending on the client's environment (and our contracts) it is the duty of the client to use these monitoring tools for sensoring the health of our servers and applications.