Like Arzam said before this is a developing field, so the utility and functionality is bound to evolve and improve in next few years until it achieves maturity.
Right now, the smart watches are a niche product, acting as an extension of our smart phones. They are allowing control and display of smart phone features and apps from our wrists, without pulling the phones out of pockets or bags.
In addition, they usually have some sort of accelerometers, heart beat monitors and GPS sensors to guage ones physical health and activity, so it ties in really well with active lifestyles.
Quite a few models allow to dictate messages using speech. There are quite a few games also coming out.
I really like how one could customise the watch face every day and have a new watch literally every day.
Tapatalkin' from my Sony Xperia Z3 Dual 4.15.10