Hello!
I love making homebrew pinball/coin-op stuff (and some commercial stuff too!), and I wanted to contribute something back to the ecosystem on the P3.
I started chatting with the folks over at Scorbit about integrating games made by 3rd party developers like myself, and created the following library:
https://github.com/bingopodcast/p3-scorbit-integration-public
This library allows you to build a game on the P3 with Scorbit integration. There are several touch points with Scorbit during the development process, but everything is laid out in the accompanying PDF. You simply add the GUI component (prefab included) and add the mode when your app starts.
The source is LGPL - any changes you make to the source of these libraries in your game must be contributed back for the good of us all.
Hopefully other developers will be able to make use of this and add Scorbit functionality to their own games!