If you're curious about who might be using your computer while you're away, or if you just want to make a collection of selfies each time you wake up your computer that will build up over the years, then Snoop Catcher will help you out. The Mac App Store version does flash the screen and play a sound, because it's against the app store rules to secretly take photos in any app. It's a very simple app. It will quietly take a photo every time your mac is woken up, and save it to a destination of your choosing. It will also run in the background so you won't even know it's there until you go to browse through your photos that have saved up over time. If you enjoy looking at yourself, or looking at people that try to look at your stuff, then Snoop Catcher is for you.