Most smart watches use bluetooth and need to be paired with a phone. Some have wifi and mobile data and call capability built in (watch phones).
Smart watches will be big one day but is the technology ready yet. There are issues such as battery life, bulkyness, functionality, practicality, durability to get right. Traditional always on emissive displays like backlit colour LCD and OLED are a battery drain and perform poorly in sunlight. New display technologies will be key to the success of the smart watch, Mirasol displays are interesting. It's interesting to see that Motorola are bucking the rend and going with a circular display for the Moto 360, a shape best suited to analogue clocks rather than other forms of information.