Accelerometers are found in many devices even smart phones. They are cheap but plays significant role where motion, acceleration or inertial position detection is involved. You can get XYZ accelerometer module for like $3 from eBay. Alex made a post about his experimets with MMA7361 accelerometer model. Luckily there is an Arduino library that makes programming even easier. Practically there isn’t much about reading values – simple analog read does the business.
After small experiments Alex built acceleration activated LED blinking box. He even managed to place the circuit inside dental floss container. Instead of trying to squeeze Arduino in it, he’s chosen smaller micro – Attiny45 which fits nicely. It is powered from 3V coin cell battery. Just a nice quick project for an evening.