Researchers at the University of Washington managed to design a video streaming HD camera that draws next to no power.
The main power drainer in wireless cameras is often the radio and the digital signal converter which works with the image sensor. What the researchers did was to extract these components to put them in a separate radio transmitter device. Then the camera sensor communicates directly with it's antenna with the hub's antenna to transmit the images. This results in a reduction of power consumption by more than a thousand times.
This solution allows for a video stream of 10 frames per second at a 1280x720 resolution up to 16~feet, and a small battery is required for keeping the camera operational. The goal is to make it completely batteryless.
Two good implementations of this technology would be in wearables and security cameras,