Sharpie
There are suggestions to use WD40, nail-polish-remover, acetone, Magic Eraser, alcohol, and many more products.
Personally, we’ve used WD40 for crayon on walls, and nail-polish-remover for ink on vinyl chairs, both with excellent results.
Ink on computer screen
Magic Eraser seems to get rave reviews from several posters for its ink-removing abilities.
note: The above info was culled from Google searches for “remove sharpie stain” and “remove ink computer monitor”. This type of “how to” info is what Google excels at. I strongly suggest googling the questions yourself to see firsthand the experience others have had with your clean-up issues, as well as a much more comprehensive list of ideas.