I' ve neveer used one, but there is a trail timer. It' s like a stop watch, you place a small string across the trail and when the string is released,by something walking through it the clock stops. The problem is you don' t know what tripped it just when. Obviously if all you see is deer tracks it was probably a deer but how big , buck or doe ect. that' s the big question. This is probably the single most treason trail cams came about because now you know the time as well as what.