AbstractSmartwatches can be used independently from smart-phones, but input tasks like messaging are cumbersomedue to the small display size. Parts of the display are hid-den during interaction, which can lead to incorrect input.For simplicity, instead of general text input a small set ofanswer options are often provided, but these are limitedand impersonal. In contrast, free-form drawings can an-swer messages in a very personal way, but are difficult toproduce on small displays. To enable precise drawing in-put on smartwatches we present a magnetic stylus that istracked on the back of the hand. In an evaluation of sev-eral algorithms we show that 3D position estimation witha 7.5×20 mm magnet reaches a worst-case 6 % relativeposition error on the back of the hand. Furthermore, theresults of a user study are presented, which show that inthe case of drawing applications the presented technique isfaster and more precise than direct finger input.
Watch my Painting: The Back of the Hand as a Drawing Space for Smartwatches