After getting XBMC Live installed on my Revo and getting my library setup, I couldn't find a simple option to have XBMC watch my video folder and automatically update my library. In place of this missing functionality, I figured I would setup a simple timed job to automatically update my library for me every hour.
Before I get started, I should note that there is an option to automatically update the library when the box is booted up which may work for some people. You can find this under System > Video > Update Library on Startup. This option wouldn't work for me though as I leave my box on 24/7 or at most just put it in a standby state.
See below for the details on how to setup a timed job (cron) to update your video or music library. This consists of installing the xbmc-send application and setting up a cron job (and enabling the EventServer).