Monitoring a sleeping subject

Apparatus for use with a subject who is a first person, who shares a bed with a second person, the apparatus comprising:

• a thin, flat motion sensor configured to be placed underneath a portion of the bed, and, while disposed underneath the portion of the bed, to:
• detect motion of the subject without contacting the subject, without contacting clothes the subject is wearing, without viewing the subject, and without viewing clothes the subject is wearing,
• detect motion of the second person without contacting the second person, without contacting clothes the second person is wearing, without viewing the second person, and without viewing clothes the second person is wearing, and
• generate a motion signal in response to detecting motion of the subject and motion of the second person;
• and
• a control unit configured to:
• identify components of the motion signal that were generated in response to motion of the subject, by distinguishing between components of the motion signal that were generated in response to motion of the subject, and components of the motion signal that were generated in response to motion of the second person,
• analyze the components of the motion signal that were generated in response to motion of the subject, and
• generate an output in response thereto,
• wherein the motion sensor comprises a mechanical-filtering element configured to reduce a response of the motion sensor to motion of the second person, relative to motion of the subject.