DXL335 accelerometer from Analog Devices, the LilyPad Accelerometer can detect joint movement as well as inclination and vibration.
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The ADXL335 outputs a 0V to 3V analog signal on each of the X, Y, and Z axis. You will need to convert this analog voltage to a gravity amount and use trigonometry to calculate a true 'angle'. If you are not looking for tilt, it is very easy to use this sensor for basic motion sensing.
LilyPad is a wearable e-textile technology developed by Leah Buechley and cooperatively designed by Leah and SparkFun. Each LilyPad was creatively designed to have large connecting pads to allow them to be sewn into clothing. Various input, output, power, and sensor boards are available. They're even washable!