Interestingly, the Dash uses wi-fi controlled by the setup app to be configured with an Android phone, but because the app can't control the wi-fi on an iPhone it uses ultrasonic signals: https://www.amazon.com/gp/help/customer/display.html?nodeId=... You may need to increase your iPhone volume, since Dash Button uses ultrasonic tones to sync with your iPhone during setup.
That's how the Furby Boom is able to interact with the iPad app ... only problem is, I can still hear the damn noises despite being 35!