Infrared Sensor Camera combo
an Infrared light sensor, typically used to turn lights on outside the home, in conjunction with a camera & detection software will help identify humans, as few things with that size IR print would be anything else in say a shopping center or business foyer, maybe a country carnival or Easter fair would have animals such as cows & horses in view - Dogs would be low to the ground and could be detected by the software.
just depends on the fineness of the IR sensor to differentiate individuals, tho as it would be working with camera & softwate it could be worth a try
Biting the hand that feeds IT
