I made the SmartLCD Case http://www.thingiverse.com/thing:80065 but it was missing a button so that you could push the the software kill switch. So I made this add-on button extender. Now when things go crazy I have an instant way to stop everything.
Just print, insert into front of case while it faces down then add the SmartLCD board and back panel on top. Since all I had was white ABS plastic, I colored mine red with a permanent marker.
When you push the button it shuts down everything instantly and goes into a do nothing loop. The LCD display freezes so you can analyze what was happening. You need to reset the processor to get things running again.