Peter Hopton of Sheffield University, UK, says his idea could save a fortune in energy bills and significantly reduce people's carbon footprint, particularly if they also wash their feet.
It has been released onto the market by his company, VeryPC. It uses open source face detection software linked to a webcam. The software monitors the presence of someone's face in front of the screen and reacts to it.
Now ordinarily people switch their computer to sleep mode after a set period, but many users override this because it kicks in if they are reading a book or watching a long film.
Hopton points out that once the settings are installed few people ever change them. His gizmo will sort that problem out, he claims. No word on price yet.
VeryPC has been busy tinkering with the University of Sheffield's supercomputer to make it even greener.