Google patents tech that take pictures when it sees finger frames
 

The camera on a head-mounted wearable sense where the user's fingers are positioned and take a photo when you make one of those finger frames. The wearable's camera would always be looking for fingers to pop up in its view and when it senses them it will capture a photo.

The patent also said that the device can change the orientation of the image based on the positioning of the users hands. If they made a circular "O" shape with one hand, they would end up with a round picture. And on using two hands to frame a rectangular portrait the camera could take a portrait photo.