Spark Fun Electronics took apart the Nike + iPod sensor to see how it works, and the internals are surprisingly simple (or so they say, it looks pretty complex to me). Instead of an accelerometer, the sensor uses a piezoelectric sensor to monitor how long your weight is on your foot (the faster your run, the shorter amount of time spent on one foot). Their goal is to use the sensor as an RFID transmitter, allowing you to do a variety of things (such as open doors or turn on lights with RFID switches) without having to swipe a card like a traditional RFID transmitter. Even if you donâ€™t intend on hacking your own sensor, itâ€™s an interesting peek inside the workings of such a complicatedly simple device.
[Via: MAKE: Blog]