Hi nyjan,
Thanks so much for IdleKeys!! As you are thinking about starting the work from ground up, I think we can use the CUE SDK, as it will eliminate a lot of issues with the current version (taking the focus when activating, manually setting an IdleKeys profile, etc.)
I am looking into the CUE SDK and from my initial understanding, selecting all the keys and turning them off (or black) at a selected interval and switching back to previous state when key press should be pretty trivial. Please let me know if I can help in any ways. I have almost no experience with C#/.net but maybe we can figure something out to work together.
Thanks again.