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Hello elyssam13; If you want to try an input source with a much more sensitive and wide range input you might want to look at a peizo=electric chip or array of them. The same chip that is ised as a siren, requires a +/- connection and is, by all rights, almost pure capacitance. Any vibration causes a shift in voltage like a microphone but is far more sensitive with an ADC. An array of them in a plastic baggie could be placed in the floor of the holding area. All movement, breath and even the heartbeat could be detected and easily discerned by the voltage and repetition. Similar stuff is used in medical for detecting possible SIDS with human babies. This is a crude use of the tech but it may help you in research. Best of luck.