Mac: It's a little annoying when you're reading a long article (or just spacing out) and your computer cuts to the screensaver because you haven't touched the mouse in a while. Should I Sleep is an app that keeps your display from going to sleep as long as you're sitting in front of it, using facial recognition to detect your presence via the webcam.
Before your Mac goes to sleep (or to a screensaver), the app quickly checks your webcam to see if you're still sitting in front of it. If you are, Should I Sleep prevents the computer from sleeping.
Out of the box, that's essentially all it does, but you can buy some in-app purchases to get more options, including detecting any motion from the camera, an external display, or sound activity. The face detection alone works just fine for most purposes, and it's free. If you find yourself constantly reaching for the mouse or keyboard before your display goes to sleep, Should I Sleep is a handy program to have around.