Python OS is a complete replacement for the default user interface on the Raspberry Pi. It is intended to be used with a touchscreen attached. It includes a suite of apps and a marketplace for downloading more.
It is programmed entirely in Python using Pygame for graphics. A 3D printable case is on the way as well.
Why should you be interested?
This framework provides a simple and efficient way to write responsive touchscreen apps for the Pi. This can be integrated into existing projects or used on its own. The pyos framework provides a wide range of UI components that can be used to build complex applications.
As of v1.2, Python OS supports scaling to any screen size.