Most popular are the Pebble, the MetaWatch and the Sony SmartWatch.
Those are really cool gadgets, giving you a flavour hint of the future. But let's be realistic, those smart watches may not be so smart after all.
The battery life is ridiculous. Having to charge once or twice a week a device that will give you time, 90% of it's useful usage does not make sense. For the same price, you can get a way better looking watch that will give you time and some prestige... Yes, the features, that's the whole idea behind those devices.
You're receiving a SMS on your smartphone and your watch will show it to you. It can even vibrate so you won't miss it. You look at your watch, see the message and... And? You grab your phone to reply. Same thing for emails, Facebook, Twitter, etc... Essentially, the device that should free you from your phone's notification won't do it after all. Let's be honest: if you want to be notified at all cost, it's probably because you'll reply to the message anyway (or like it).
For incoming calls, it can be a bit different. The Pebble and the MetaWatch let you see who's calling... And... And? You'll grab your phone and answer the call. The Sony SmartWatch let's you answer the call in a hand-free mode, meaning that people around you will hear your conversation... So you'll grab your phone anyway to keep your privacy.
Other features are available, but do you really need them. Weather: Look up, you're probably already outside. Wall Street: if you're a broker, maybe useful. Calendar: you're phone will alert you anyway and you probably already checked your day in the morning on your phone.
Basically, a smart watch is just adding a step to the process of managing your smartphone life. That's all!
It's cool, it's nice but not smart. Smartphones can already be configured to notify you only when appropriate and call filtering can also be achieved in a way or another. If I cannot interact thru the watch to prevent me from reaching for my iPhone, there is no point getting another layer in the process and draining more battery life. Filtering calls does not happen so often. Waiting for an important message, you'll have your smartphone in front of you, ready to reply.
When you can make it wait until you have free time, there is no point of being distracted while you're busy. Those devices are for gadgets lovers and social media freaks.