The Mystery of IMU
To measure the movement of the singers head we had the idea to use a Wiimote controller. The Wiimote is cheap and easy to use on a Mac for example by using Osculator to communicate with the Wiimote and the computer. Once the movement data is in the computer you can easily route it via OSC to other applications. In our case we use Isadora. The problem with the Wiimote is that it contains linear accelerometers that measure acceleration along the axes, but no gyroscopes. So it is impossible to measure linear movement along the axes. Recently Nintendo released the Motion Plus extension which ads the gyroscopes to the Wiimote. Only there seems to be no software written yet to measure this data.
So what to do now? Jan Klug gave us the names of possible sensor hardware which we can use. During the research throughout the web I discovered that the device we are looking for has actualy a name. It is called a Inertial Measurement Unit (IMU). For now I have two solutions. The first one is to buy a complete but quite expensive system with the Orient3D sensor of Infusion Systems, or the make one myself with Arduino and connected accelerometers and gyroscopes. The last one is pretty hard and time consuming but way more cheaper. You can buy the sensors online at SparksFun. I found some people who are quite active with this.