Nuance is a new device adding multi-touch force detection to the iPad touch screen. It communicates with the iPad using the audio jack input. Force information is sent at an audio rate using analog amplitude modulation (AM). Nuance provides a high level of sensitivity and responsiveness by only using analog components. It is very cheap to make.
Nuance has been developed in the context of a larger project on augmenting mobile devices towards the creation of a form of hybrid lutherie where instruments are based on physical and virtual elements.