reverse motion sensor

Hi!

I'm very new to arduino and I was wondering if there was a motion sensor that activates when it DOES NOT detect movement, as opposed to one that detects movement?? Or is there a way I can reverse program it?

I want to make a pair of glasses that vibrates/makes noise when it detects that your eyes have been shut (stopped blinking) for a duration of time.

Any help would very appreciated!

Standard PIR motion sensors give a signal that is HIGH or LOW if motion is detected. From a programming point the reverse is simple an inverting operation (!). Regarding your intended use you probably cannot use a motion sensor but need a motion detection with a camera. The computational overhead this solution involves moves an Arduino out of the game. Getting everything into a pair of glasses is, heavily understated, challenging.