Tim takes his hand and puts Billy's index finger on a flat button under the dial, prompting a white mock up of a fingerprint on the dial, highlighted partially in red. He shifts Billy's finger a couple of times until the print is completely red and blinking.

"So, When this goes live on the market, you'll be able to use the watch to quickly make emergency calls; just tap and say if you want the police or a medic, and you'll get one sent via GPS. But this will let you hold the button with your finger and let me know you've seen something... bigger."

To demonstrate, Tim holds Billy's finger down on the button again. There's a soft beeping coming from his bag.