Contact mics are wonderful little devices that can be used to record pretty much anything that sends off any kind of vibration. I first encountered contact mics through my encounters with Creme Dementia and his circuit bending group/band CMKT4. Contact Mics can be made using a piezo transducer (typically found in buzzer alarms, smoke detectors, and many other things).
These can be made standalone in numerous ways, or attached permanently to the object you want to amplify. I have attached them to different objects such as washboards, hand saws, cog wheels, tumbler style music boxes, thumb pianos, door stops, and my favorite made to date, an aluminum diddley bow.