On the pi board p6 near the power socket has two holes, I soldered two pins in here and bought a cheap pc reset button switch off eBay which I attached to p6. Now if the pi hangs or I need to turn it off I can hold the switch in and switch off the pi at the cigarette socket or press it quickly to reboot.
I have also added it to the top and also cut a little hole to let the heat out.
