Arduino(or similar) Vibration sensing unit

What I would like to do is build a vibration sensing unit using an arduino (or similar) and a ADXL345 3 axis accelerometer. I will be placing this unit on a piece of machinery to measure when the machine stops vibrating. This is the steps that I would like to use to and the additional features that I would like: 1. a digital(on/off) output to signal that the unit is below the vibration threshhold( on when below vibration threshold, off when unit is vibrating and vibration is above threshold). This will be used to hand off the vibration status to a separate piece of equipment. 2. an led signaling when the unit is below the vibration threshold(on when below threshold, off when above) 3. a potentiometer that will let me adjust the vibration threshold. One machine may have more vibration than the next machine, so I need to be able to easily adjust the vibration threshold via the potentiometer.