Methods, apparatus, systems and articles of manufacture to count people in an audience are disclosed. An example system includes means for transmitting a control signal to a portable device a threshold period of time after a person logs into a people meter separate from the portable device. The control signal causes the portable device to begin collecting location information and proximity information. The system also includes means for analyzing the location information to determine a location result indicative of a location of the portable device. The system further includes means for analyzing the proximity information to determine a proximity result indicative of whether the person is near the portable device. The location result and the proximity result collectively define first presence information. The first presence information indicative of whether the person is present in a media exposure environment associated with a media presentation device.