1. A method, comprising: generating, based on a first output signal from a first sensor, a first parameter value representative of a first property of a media device; generating, based on a second output signal from a second sensor, a second parameter value representative of a second property of the media device; calculating a first state probability that the media device is presenting media provided by a first source based on a first conditional probability associated with the first parameter value and a second conditional probability associated with the second parameter value; calculating a second state probability that the media device is presenting media provided by a second source different than the first source based on a third conditional probability associated with the first parameter value and a fourth conditional probability associated with the second parameter value; and generating a state identifier by comparing the first state probability and the second state probability.