Note that the sensors can also provide side-channel information gleaned from measurements not necessarily designed to directly measure the element in question, such as: an accelerometer; a gyroscope; an ambient light sensor; a magnetometer; a barometer; a proximity sensor; a thermometer; and an image sensor.

Moreover, the data obtained from the sensors can be related to the interaction of multiple devices, such as: (1) the presence of different devices within wireless range or on the same local network; (2) the relative signal strength, noise, packet loss, bandwidth readings, or other statistics among multiple devices, or between a mobile device such as a mobile phone and a fixed device such as a wireless access point; (3) a combination of audio data from multiple microphones that measure ambient noise; (4) audio signals generated by playing sounds on speakers and listening for those sounds or echoes of those sounds on nearby microphones; (5) signals obtained by recording ambient light data from multiple light sensors; and (6) signals that indicate when a device is attached/paired with another device, or comes into range or communication with the other device (or when a device is detached/unpaired or goes out of range).