What do mouse and keystrokes have to do with eyestrain, though? I guess it could be an indicator on how active you are using your computer, but I could imagine plenty activities that involve using your computer without actually interacting with it.
Can you provide any other examples which does not include mouse & keyboard?
I think mostly Developers, Designers & Gamers spend their time the most in front of the computer & need breaks.
For me, this app worked immensely well because I for the past couple of weeks I've been coding for 9+ hours without a lot of break (not more than 5 minutes) & it hurt my eyes & also there is a lot of headache too. Now I don't have to consciously remind myself to take breaks. AFK takes care of that for me :)