This document gives an overview over already researched approaches to sense finger-based keystrokes on physical or virtual key-boards. Since the typical way of finger-based input-methods measures the press of a key or use electric discharges on touch sensitive surfaces, there are also other information released during a keystroke, which can be used alternatively. On the following pages, some promising methods are introduced and discussed with respect to their advantages and disadvantages as a replacement for common text input methods. Hereby, the document focuses on keystroke sensing by device accelerations, acoustic emanations, video and wifi-based approaches. As we will see, methods of acoustic sensing reaches already very accurate and robust solutions, but also other techniques have remarkable solutions and results.