The main point of this chapter is that a particle system can be used for vastly different things. Perhaps this is not the most stunningly clever idea you've heard today, so let's instead summarize the main points of the whole book, regardless of small implementation details.
In this lengthy write-up, we barely scratched the surface of what can be easily done with Python and Kivy. The realm of possibilities is vast and diverse:
Utility apps for desktop and mobile
Applications for content creation, be it a graphical or text editor, possibly even a sound synthesizer
Networked apps used for chatting, other ways of social networking, and remote control programs
Video games
Over the course of this book, we also highlighted some useful principles of working with any new technology efficiently:
Apply your experience from other problem domains, such as web development. Kivy is different, but it's not that much different; many approaches are actually reusable between substantially different environments...