It's interaction with homekit/car play. The Internet of things is slowly gaining momentum and will be huge once a standard has been set. I envisage the apple watch being contextually aware. It will anticipate when you are near your house or car and give you options over locks, heating, lights even switching on your kettle. This combined with Siri will result in a remote control for your life. The apple watch will always be on your wrist so there will be no hunting around for your phone. This is how I see the apple watch changing my life.