People trip over cables all the time.
People also have peripheral vision which is very sensitive to movement (something to do with spotting dangerous beasties lurking in the long grass).
Today’s invention is a device which plugs eg into a USB port on a laptop and which flicks the power cord every few seconds.
This allows passers by to become more aware of the moving cable and step over it safely.
(A better version would be incorporated into plugtops in general, but that would require somewhat more complex design).