A peak flow meter, breathalyzer, and pulse oximeter for use with a mobile device, such as a smartphone, are disclosed. In one embodiment, the peak flow meter receives air flow from the patient, converts it into an electrical signal using a pressure transducer, and transmits the signal to a mobile device over an interface. In another embodiment, the microphone of the mobile device is used to directly receive the airflow, and the mobile device converts the airflow into an electrical signal indicating the peak flow. In another embodiment, a breathalyzer receives air flow from a patient, converts it into an electrical signal using a sensor, and transmits the signal to a mobile device over an interface. In another embodiment, a pulse oximeter measures oxygen saturation in a patients blood and transmits an electrical signal for that measurement to a mobile device over an interface.
