So what I’ve done is take an old (broken) battery grip that I had lying around (for my Canon 5D Mark II), and made a few modifications to it so I could fit the Raspberry Pi SBC (Single Board Computer) into it. I left a few holes in the case so that I could get at the USB and network ports, and video port. it’s a fully functioning computer with a Linux Operating System (Raspbian), has 2 USB, network, video, HDMI and GPIO.
Wireless tethered shooting – attach a Wifi dongle to the USB port, so I can transmit pictures to a PC or tablet PC as I’m shooting.
Attach a USB memory key or hard drive so I can back up the images on the camera.
Remote control the camera using a PC, tablet PC or smartphone (from anywhere in the world).
Intervalometer – take a picture every few seconds for those high-speed sunset sequences, including exposure adjustment as you go.
On-the-fly image conversion for faster previews on remote display device (iPad, etc).
Add a small LCD display to give status, allow user input via buttons, etc.
Trigger camera via shutter release port, also allows waking up of sleeping camera, which cant be done via USB.