It may happen that your system is slow for some reason, it may fail completely, be under an attack, it can even have a troyan and you do not even know. I found a script recently which integrates into your system via a daily cronjob. It uses logrotate. So it is basically just another log which contains information on the system status and on information found in other log files. The best is: You can add your own commands, you want to be run every hour. It might be your HDD raid or a special server configuration that you want to monitor.
I found the information on this Japanese website: http://d.hatena.ne.jp/Ubuntu/mobile?word=*[resource]. Just in case it would disappear I also put the necessary files on github as a gist: http://gist.github.com/299632.
I think it is quite self-explanatory. In case you have questions, I might post more details on how to set it up and use it.