iStat Server is an app that can monitor your system. It is the server-side app that powers most of the functionality of the iStat for iPhone app. This app allows you to monitor your Mac from an iOS device, like the iPhone, iPod Touch, or iPad. The server is absolutely free, but the iOS app is $0.99. It is still very cheap and it works very well.
iStat Server uses an installation wizard to install the necessary components. It is a brief process, though. After the sensors have been installed, the console will show up. It consists of a window that displays a numeric code that you will have to use on your iOS device to connect to the server. You can reset this password and get a new one by clicking on the "New Passcode" button. Every time you do that, though, you will be asked for your system password.
iStat Server listens for connections on the port 5109. I don't see an easy way to change the listening port. So, you might have to do some port forwarding to get this to work if your router doesn't support uPNP.
Once everything is set up, you will be able to monitor the status of your CPU, disks, memory, up time, averages, etc., from a distance, on your iPhone.
