Hello! I've finished prototyping my in-line micro-USB power switch for the Pi. I think it will be useful for people running headless setups or who just would prefer to have a physical on-off switch so they can quickly and safely shut their Pi down when not in use. I programmed an ATtiny85 to communicate with two GPIO pins; a tiny script runs on the Pi and when the physical switch is pressed, the Pi starts a sudo shutdown sequence. Once that is complete, the ATtiny85 picks this up and cuts power. Press the switch again and everything boots up as normal. I've also programmed the switch to detect when a shutdown has been initiated via software and it will cut power safely. Hard reset is also available on the switch.
I've redesigned the switch to use MOSFETs which has shrunk the board by about 40%. I will post an updated photo and video once the new circuit boards are printed.
You can see the video and info at:
http://www.kickstarter.com/projects/1312527055/micro-usb-on-off-power-switch-for-raspberry-pi
Hopefully some of my fellow Pi users can find use in this addition!