There are separate Braille keyboards for people with visual impairments. However, a simple, portable solution had not yet been developed for smartphones. This situation has changed thanks to a bachelor thesis at the Vienna University of Technology. Johannes Strelka-Petz (research area: Multidisciplinary Design & User Research) has now developed a Braille keyboard which can be simply mounted onto the back of a smartphone. The mobile Braille keyboard called "Oskar" enables people with visual impairments to quickly type in messages when they are on the go. The keyboard can be glued onto the back of the smartphone or fastened using magnets. The device communicates with the smartphone via a low energy Bluetooth connection. The mobile Braille keyboard "Oskar" is an open source project. The plans and programme code are available online at no cost.