Notifications are the No. 1 reason I would feel lost if I ever forgot to wear the Apple Watch.

Having now used the Apple Watch for some time, I have a good idea of how I use it and the apps that are most valuable.

Interestingly, among those early adopters who love Cupertino's smartwatch, their pick for its killer app varies greatly. For instance, my wife's killer app is "Find my iPhone" since she is always misplacing it. She also loves using it to communicate with our granddaughter, who is in junior high and also has an Apple Watch. For others, it is the activity tracker and step counter.

But for a specific group of users known as knowledge workers, myself included, the killer app seems to be notifications. I got hooked on notifications when I started using the original Samsung Gear and Moto 360 smartwatches. So when the Apple Watch came out, I knew it would become an important device for me.

Indeed, since I've had my Apple Watch, notifications are the No. 1 reason I would feel lost if I ever forgot to wear it. I tailored the notifications for my particular needs, from news alerts from CNN, AP, and ESPN to tweets that are tied to key people I follow. There are now thousands of apps with Apple Watch notification capabilities, but I find these to be the most important to me. 

During CES, I talked to dozens of Apple Watch users and they told me the same thing, while those on wearable panels mentioned them, too.

What I think appeals to them is based on two key things. First, since it is connected to their iPhone, it sends them pertinent info or data on the wrist so they are not always taking the phone out of their pocket. It is much easier to evaluate an incoming call on your wrist. I only take calls from family, friends and my staff. All others go to voicemail.

For knowledge workers who are information addicts, meanwhile, notifications save them from constantly peeking at their phones.

It can also help you save or make money, I had a friend tell me that he tracks three of his key investments via the Apple Watch. He was once notified of a major swing in one of his stocks and he immediately acted on it, making a major profit. 

I suspect that by the end of 2016, it will become clearer that notifications are a big part of why people buy a smartwatch. Of course, the big question is will people spend $350 or more for an Apple Watch or competing device if they only use it for alerts?

As of now, early adopters seem to be saying yes. But since killer apps are very personal and subjective, Apple will need to work harder with developers to create even more innovative apps that make its wearable a smart purchase.