Beacon devices transmit wireless beacon messages to alert an application on a mobile phone of the Beacon device's proximity. Contemplated beacon devices may also include an ultrasonic emitter and one or more microphones. The ultrasonic emitter may be used to complement other beacon operations, communicate information to a user mobile device, and monitor the beacon device's environment. Ultrasonic data may also be used to determine if a person or object is in proximity to the beacon device. Short echolocation travel times may be used to indicate that a user is “touching” the beacon device. Inter-beacon device communication may also be accomplished using the ultrasonic emitter.