Apple Mac OS X includes Photo Booth, an application for taking photos and videos with the built-in camera (if available, of course). Photo Booth can also add effects while taking a picture or video. In the recent version (Yosemite), Photo Booth is able to detect faces and adds the effect to every face detected in the image/video, see this example I found on YouTube:
Photo Booth applies effects in real time and cannot add effects to already recorded footage.
Is there any video editing software or video effects software available which can do this, i.e., add an effect similar to Photo Booths face detection based effects to existing video?