It started as a simple weekend project based on an off-hand comment someone made in a security professional chat I'm in. I had used duress words in military and translating the concept to a PAM seemed like a fun exercise. Also supports my current shift towards swapping careers from pure software engineering to cyber-research or cybersecurity generally. So in the end, it was a weekend project that served a dual purpose as a resume stamp.
The design use case I had in mind was more benign; such as corporate espionage or journalists getting their devices confiscated (maybe keep a sticky note on the laptop that has a duress password on it as a red-herring). Comments to the effect that law enforcement would image a device are very relevant as any competent law enforcement agency should have their staff trained to get the device fully powered off and hand it to someone that can maintain a chain of custody and get a golden image for use in potential criminal charges.
One thought I had was to apply this to SSH auth for honeypots and if a rockyou.txt password is attempted it runs some routines that aid in crafting the honeypot before the intruder drops to a shell prompt. Another even more light-hearted implementation could be you have password X is the one you login to normally and your "duress" password Y just clears your browser history and is the one you give your spouse for when they log into your computer :). I'm sure there's use cases in the full spectrum and with it being a relatively simple implementation with user generated scripts, it'd be easy to extend to any potential use case.
In any case I'm glad it prompted such a good discussion. Feel free to submit issues if there are particular feature requests or bugs that one might run across. Additionally if there's a PR up, I'm currently the only dedicated dev on the project and welcome anyone that wants to review my PRs; always prefer a 3rd person review even on my own projects. I created a demo video using Pushover and in the process of doing the demo uncovered some bugs that I patched as well as some fixes to the documentation. Again, glad you all found this interesting and humbled it fostered such a good discussion.