1. Apparatus comprising in combination: an illumination source for emitting light that travels from the illumination source to an object by diffuse reflection, a sensor for taking measurements of light that travels from the object to the sensor by diffuse reflection from a surface, which sensor includes a phased array, and one or more processors for calculating (based at least in part on the measurements) motion or size of the object, which object is visible to neither the sensor nor the illumination source.