One of the neat things about Apple Watch is the ability to send digital touches to friends who also have Apple Watches. To use this feature, press the side button to bring up your friends list, then select a friend who also has an Apple Watch.
Tap the center button to start a digital touch session with your friend
There are 3 forms of digital touch:
Sketches- To sketch, just draw on the screen with your finger. To change the color of your sketches, tap the colored dot in the upper right hand corner and you'll be presented with color options.
Taps - Instead of drawing you can tap the palette and those taps will be mirrored to your friends Watch.
Heartbeat - To send you heartbeat, place two fingers on the palette and rest them there. You'll see a heartbeat animation and feel what will be sent to your friend via Taptic engine.