According to a few reports on the web wires, OS X Mavericks still has a few more power-saving secrets to show off. The latest to be discovered was found by a developer poking around, and discovering a potentially creepy feature.

Moshen Chan posted on Twitter that the iSight cameras built into many Macs were being used to monitor users, but he was only half right. It turns out that one of the sensors next to Apple’s web camera, the ambient light sensor, is in fact what’s being used to monitor users.

It gets less creepy, though. Rather than keep track of you for nefarious purposes, the ambient light sensor can detect when users are not in front of their computers. With this information the OS can instruct the computer to dim, or power off, the display when it’s determined there’s nobody behind the keyboard. Alternatively, when vague movement is detected, Mavericks can keep the lights on for longer.

A small touch, but one that’s convenient when you’re at your desk, and power-saving when you’re not.