A dedicated voice control button on the Plantronics Voyager 5200 Bluetooth headset easily activates Siri, GoogleNow, or Cortana. (rainydaymagazine.com)
Connect via USB or Bluetooth, then press and hold the voice control button on your steering wheel. (apple.com)
To do so, press the voice control button, and wait for it to beep, then say «Disc.» (yourmechanic.com)