The ADXL335 is an inexpensive accelerometer that is very easy to use. As an example, I connected an ADXL335 to a Teensy, and fed the MIDI data to Live.
The ADXL simply outputs an analog voltage for the X, Y and Z axes, so interfacing such a unit with a Teensy board is very straightforward.
The Teensy code is as follows:
This code is a very basic example and could be improved upon by:
* measuring min and max values to calibrate during runtime
* smoothing out data
* allowing the user to scale the data in certain ways
* allowing the user to mute one or more axes