Ubisoft has been developing YouUp, a technology that relies on face detection in order to insert virtual objects into web camera feed, for the last couple of years. An early demo of YouUp can be seen below -
Following the integration with Messenger, users can now have video chats with an added fun factor (if this is your sort of fun). As Yves Guillemot, chief executive officer at Ubisoft puts it (source):
YouUp will allow users to truly enjoy chatting via webcam. This playful application is fun, offering disguises and hilarious 3D effects that adapt easily to each user’s face
I know, it's not a ground breaking technology (though it seems to be well implemented), but it's further evidence that augmented reality is creeping its way to the mainstream.
(download it here (in French))