Apparatus is provided, including a sensor configured to sense motion of a subject and generate a motion signal in response thereto. The apparatus includes an output unit and a control unit. The control unit is configured to: (a) analyze the motion signal, (b) at a first time, determine that the motion signal is indicative that the subject is likely sleeping, (c) at a second time following the first time, determine that the motion signal is indicative that the subject is likely no longer sleeping, and (d) in response thereto, drive the output unit to alert a clinician if the subject is at an increased risk for falling out of a bed. Other applications are also described.