Boot to GUI USB disk creator
This is a script that creates from scratch a Debian stable image that boots, starts up X and launches a single GUI application. There is no shutdown.
To create an image insert a USB disk, check what its device name is
(/dev/sdd assumed below) and then run:
sudo ./createimage.py /dev/sdd
Boot a computer with the USB stick to use it.
This script probably only works on Debian and its derivatives like Ubuntu.
The application is run as root.
The application is implemented in Gtk+ 3 and Python 3. If you want some other framework, you need to change the dependency list and the application's install command.