A self-mixing interferometry sensor module includes a light emitter and an electronic control unit coupled to the light emitter. The light emitter is configured to emit coherent electromagnetic radiation out of the sensor module. The light emitter is also configured to undergo self-mixing interference (SMI) caused by reflections of the emitted electromagnetic radiation from an object outside the sensor module. The electronic control unit is configured to detect a change in an electrical property of the light emitter caused by the SMI. The electronic control unit is also configured to determine from the detected change a movement of the object outside the sensor module. The electronic control unit is further configured to generate an output signal that includes information of the determined movement.

A sleeve or case for a mobile device, such as a smartphone or tablet or other types of hand-held device or mobile smart device, has a sleeve part for at least partially enclosing the mobile device and an input device arranged in the sleeve part for controlling the mobile device which can be received in the sleeve part. The input device includes a movable control element and a magnetorheological brake. Any movement of the control element can be selectively damped by way of the magnetorheological brake.

A sleeve or case for a mobile device, such as a smartphone or tablet or other types of hand-held device or mobile smart device, has a sleeve part for at least partially enclosing the mobile device and an input device arranged in the sleeve part for controlling the mobile device which can be received in the sleeve part. The input device includes a movable control element and a magnetorheological brake. Any movement of the control element can be selectively damped by way of the magnetorheological brake.