> their small usable size
That is THE “biggest hurdle,” because with current technology, it’s not possible to squeeze an adequate level of “smartness” into something that is called a “watch.” That’s why devices that are called “smartwatch” have not been massively popular (so far); they are not smart enough to be worthwhile.
Apple blows away this limitation by requiring the Apple Watch customer to have an iPhone (5 or later). Because Apple Watch is “powered by iPhone” (and integrally connected), it can do things that far surpass the basic functionality of any “independent” device that is currently called a “smartwatch.” And because iPhone is doing the heavy-lifting, third-party developers can expand the functionality of Apple Watch beyond what Apple provides as built-in features. Other smartwatches are mostly “what you buy is what you get forever” (the equivalent of old-school “feature phones”).
Imagine what Apple and its army of developers can create for the iPhone experience using Apple Watch’s always visible secondary screen, touch (and “digital crown”) input, “haptic” feedback, and multiple sensors. iPhone customers will consider it a must-have “upgrade” for their iPhone. Maybe not all of them, but if even 10% decide to get an Apple Watch, it’s a HUGE success. 20% (just one in five customers with iPhone 5 or later) would be astonishing.
And the best part is that ONLY Apple can create a (viable) product that works like Apple Watch.
Source : http://macdailynews.com/2015/01/06/apple-watch-wont-wear-out-its-welcome-the-wearable-internet-of-things-market-has-been-waiting-for-apples-lead/