Interesting that this was implemented as a standalone C++ Application. I was expected this to be a vim script like program, which would be more desirable as it would pick up on custom defined shortcuts in my ~/.vimrc.
Emacs has something called Keywiz https://marmalade-repo.org/packages/keywiz which will gather your keybindings (including custom ones) and ask them back to you as a quiz.
Not as cool as this but I used to play it back in the day and learnt quite a few neat tricks from it.