Make your own motion sensor
I remember this thing from the movie The Rock when Nicolas Cage is braking into the Alcatraz. I am talking about the motion/vibration sensor in it's very simple build. I remember making this thing 10 years back in a similar way. My version had a wire hanging from above and at the bottom there was a wire-ring. When it was tilted, the hanging wire made contact with the ring and voila! Anyway, this version is much more sensitive. Aside from this one, there is a tilt sensor that has a metal ball in a tube. It is some kind of mercury-less tilt switch.