Low power virtual reality presence monitoring and notification

A method of notifying a virtual reality (VR) headset user to the presence of a human or animal comprising: using thermal sensors (211, Fig. 3) to detect activity near the user 403; determining whether the thermal activity is moving 405; analysing the thermal activity to determine whether it is characteristic of an animate being 407; and generating a visual alert (505, Fig. 5) via the headset 409. The visual alert to the user may be one of: an outline image; a thermal image; a photographic image; or a VR character. The pose and location of the source of the thermal activity may be continuously monitored and the visual alert updated accordingly. The VR headset may also generate an audio alert. The sensors may be thermopile sensors. The system ensures that the VR headset user is alerted to, but not startled by, the presence of a real world animate being.