I know with other distributions of Linux you can use fingerprint readers to login instead of using a password. Is it possible to do this on the Raspberry Pi using like a 4x4 membrane keypad with my own program?
To interface with the main input, you could write a python program using the GPIO and the
uinput module. This makes it easy to create your own keypads. Install with the command
sudo pip install uinput. For info on the module, please see here.