The company Microsoft has developed Skinput, a technology that appropriates the human body for acoustic transmission, allowing the skin to be used as an entry surface. In particular, we resolve the location of the finger taps on the arm and hand by analyzing mechanical vibrations that propagate through the body.

We collect these signals using a new series of sensors used as a bracelet. This approach provides an always available finger input system, naturally portable and in the body. We evaluated the capabilities, the precision and the limitations of our technique through a user study of two parties and twenty participants. To further illustrate the usefulness of our approach, we conclude with several proof-of-concept applications that we develop.

Devices with computational power and significant capabilities can now be easily carried over our bodies. However, its small size typically leads to limited interaction space (for example, tiny screens, buttons and jog wheels) and, consequently, decreases its usability and functionality. Since we can not simply make buttons and screens larger without losing the primary benefit of small size, we consider alternative approaches that enhance interactions with small mobile systems.
One option is to opportunely appropriate the surface of the environment for interactive purposes. For example, Scratch Input is a technique that allows a small mobile device to convert tables on which it rests on a finger-sized sign canvas. However, tables are not always present, and in a mobile context, users are unlikely to want to bring the appropriate surfaces with them (at this point, it could also have a larger device). However, there is a surface that has been overlooked as an entry canvas, and one that happens to travel always with us: our skin.
Taking advantage of the human body as an input device is attractive not only because we have approximately two square meters of external surface, but also because much of it is easily accessible by our hands (eg arms, upper legs, torso) . In addition, proprioception (our sense of how our body is configured in three-dimensional space) allows us to interact accurately with our bodies in an eye-free manner. For example, we can easily shake each of our fingers, touch the tip of our nose, and clap our hands without visual aid. Few external input devices can claim this precise input feature without eyes and provide such a large area of interaction.