Wearables are portable devices, usually worn on the body, that can generate, exchange and process data. Smartwatches for example not only offer some of the functions of a smartphone, like messaging or controlling connected devices such as bluetooth speakers, they are also equipped with various sensors that can measure bodily functions. As sensors and processors get smaller and more powerful, they can be integrated into different kinds of items: glasses and shoes for instance, or materials like textile. These developments expand the possibilities to use technological devices close to the body, or even implanted in the body. Although the functions of wearable technology can be diverse, the close proximity to the body makes this type of technology particularly relevant for health and fitness purposes.