A wearable computing device includes a display, a motion sensor, and a controller that: defines a pose of a simulated input object with selectable input elements; using the motion sensor, determines current poses of the display, and for each pose: (i) based on the pose and the pose of the input object, selects a portion of the input object, including a subset of the input elements, and (ii) renders the portion of the input object on the display; for at least one of the current poses, detects a simulated key press associated with one of the subset of input elements, and generates input data corresponding to the one of the subset of input elements. The device includes a housing containing the display, the motion sensor, and the controller; and a mounting component, coupled to the housing and configured to removably affix the housing to a forearm of an operator.