An apparatus configured to sense presence and motion in a monitored space, the apparatus comprising: two or more thermal sensing devices (424a,424b), each of which is configured to produce a direct current output that is sustained at a level substantially proportional to an amount of thermal energy being received at the thermal sensing device; and a lens array coupled to the two or more thermal sensing devices, wherein the lens array comprises a plurality of lenses, each of which is configured to direct incident thermal energy from a respective one of a plurality of optically-defined spatial zones (322a, 322b, 322c and 322d) located within the monitored space onto the two or more thermal sensing devices; wherein the apparatus is further configured to receive incident thermal energy at a lens array from the plurality of optically defined spatial zones located within the monitored space, direct the incident thermal energy received at each lens onto the two or more thermal sensing devices that are optically coupled to the lens array; and produce, with the two or more thermal sensing devices, a direct current output that is sustained at a level proportional to an amount of thermal energy being directed to the two or more thermal sensing devices by one or more of the lenses; receive data at a computer-based processor from the two or more thermal sensing devices; and determine, with the computer-based processor, whether there is a living being present in or moving about the monitored space based on the data received from the two or more thermal sensing devices, and wherein the computer-based processor, is configured to assess a differential signal derived from a first direct current output from a first one of the thermal sensing devices and a second direct current output from a second one of the thermal sensing devices, wherein the differential signal represents a rate of change between the first and second direct current output. two or more thermal sensing devices (424a,424b), each of which is configured to produce a direct current output that is sustained at a level substantially proportional to an amount of thermal energy being received at the thermal sensing device; and a lens array coupled to the two or more thermal sensing devices, wherein the lens array comprises a plurality of lenses, each of which is configured to direct incident thermal energy from a respective one of a plurality of optically-defined spatial zones (322a, 322b, 322c and 322d) located within the monitored space onto the two or more thermal sensing devices; wherein the apparatus is further configured to receive incident thermal energy at a lens array from the plurality of optically defined spatial zones located within the monitored space, direct the incident thermal energy received at each lens onto the two or more thermal sensing devices that are optically coupled to the lens array; and produce, with the two or more thermal sensing devices, a direct current output that is sustained at a level proportional to an amount of thermal energy being directed to the two or more thermal sensing devices by one or more of the lenses; receive data at a computer-based processor from the two or more thermal sensing devices; and determine, with the computer-based processor, whether there is a living being present in or moving about the monitored space based on the data received from the two or more thermal sensing devices, and wherein the computer-based processor, is configured to assess a differential signal derived from a first direct current output from a first one of the thermal sensing devices and a second direct current output from a second one of the thermal sensing devices, wherein the differential signal represents a rate of change between the first and second direct current output.