Retro Phone Handset for smartphone - Nothing ruins a perfectly-crafted steampunk costume quite like pulling your phone out of your trousers or skirts to take a call. Bubble of suspended disbelief popped.
Satechi Bluetooth Button - Instead of fumbling for your phone while you drive, just press the button. This one: the Satechi Bluetooth Button. Attach one to the dash & hit it when you need to answer the call, crank up the volume, play or pause.