Apple have shown the new watch to the media. This has a Taptic Engine or "Digital Touch". It allows a person's heartbeat to be transmitted as an actual bump to another person.
Image from Apple.
I designed and built similar technology for Microsoft, more here in 2005. This used an optical sensor in a mouse to measure heartbeat and transmit to another user as a haptic bump in their hand. There is no patent and all in public domain.
image from 2006, mockup but working hardware tested
Recently I have been evaluating this technology for mobile phones. All the hardware exists in mobile phones, e.g. camera and vibrator.