Shoutbox is a simple chat module with auto-refresh.
It's included in the standard Epesi source tree and installed like any other module, through Modules Administration & Store. It's a useful one to read after finishing this tutorial's core lessons — it's small enough to read end-to-end, but real enough (auto-refreshing, multi-user) to show the module/RecordBrowser/ActionBar patterns taught above working together in something you'd actually ship, rather than the stripped-down Hello World example.
Browse its source in the main Epesi repository on GitHub — search the modules tree for Shoutbox — or in your local install's modules/ directory once installed.