Returning phone calls
Answering calls is handled differently by different smartwatches. The Sony Smartwatch 3, for example, allows users to accept and decline calls on the watch while using the phone's speaker and microphone (or headphones, if plugged in) to carry on the conversation. This is useful when you're walking around with headphones on or driving when your smartphone isn't easily accessible.
Others, such as the Apple Watch, enable users to respond to and carry out conversations directly from the watch (the phone may remain in your bag). It's not the best way to answer every call, but it's useful for quick conversations when you can't reach your phone.