Get notified by notification centre when someone ssh's into my computer? I know that if I open Terminal and I type inwho, it shows who is logged in and at what time, etc. However, I am not going to be at Terminal all day and keep typing who. So, I would like a notification that appears when someone logs into my computer, or in this case, when someone ssh's into my computer. Is there some way to do this in Applescript? Thanks for your help!
Applications like Growl or GeekTool may be able to help you with this. Growl can send messages to the Notification Center or use its own notifications; when coupled with an external system application like Log Surfer, it may be able to provide the notification you seek.

GeekTool would be much easier to setup, but doesn't send info to the Notification Center. Instead, you can have it display the output from a standard UNIX command on your desktop. In particular, you could have it display the output of a 'who' command, and update that every few seconds.