What such a script, or scripts, should be doing in your environment is a question that cannot be answered by anyone but you. You may be a lone wolf or you may work from a shared cube administering bunches of systems with bunches of other SysAdmins. The distribution of duties and composition of the environment drive the specifics of monitoring software in different directions, but many of the tasks are generally the same. The tasks performed by nightowl are a good start, although I hope that your production systems are stable enough that you do not have to monitor for orphaned IPC services. Figure 2 contains the balance of general monitoring tasks I have automated myself or observed in various environments.
Automation is only a good start, though.
There are some other tasks that you need to get on your agenda. Otherwise, you will not be able to keep your new-found sanity. Take a look at Figure 3 . It contains more action items, but they fall more into the category of planning than they do automated monitoring. Many of the tasks are daily, and others, well, how often you visit them will depend on the environment in which you work and your own initiative.