OverSight is an anti-malware app that monitors a Mac's microphone and webcam, alerting a user when the internal mic is activated, or whenever a process accesses the built-in webcam.
One of the most insidious actions of malware, is abusing the audio and video capabilities of an infected host to record an unknowing user. Macs, of course, are not immune; malware such as OSX/FruitFly, OSX/Crisis, OSX/Mokes, and others, all attempt to spy on Mac users. OverSight constantly monitors a system, alerting a user whenever the internal microphone is activated, or the built-in webcam is accessed. And yes, while the webcam's LED will turn on whenever a session is initially started, new research has shown that malware can surreptitious piggyback into such existing sessions (FaceTime, Skype, Google Hangouts, etc.) and record both audio and video - without fear of detection.