In the wearable computing category a smart ring could beat a smart glass or even a smart watch. A smart belt perhaps? The ring would be great for health apps, especially sleep apps, physical activity apps.
I see the smartphone still being the center of the wearable computing universe. Just like my favorite smartphone apps I can still access from my laptop.
Battery is the biggest bottle neck in the whole equation. A good battery is one you don't worry about. There is always juice.
Wearable computing can be amazing for the global traveler. For safety, for navigation.
Google Now could use all of the above. You want the smart things to constantly be soaking data, but the display can not be constant. Otherwise those smart things get in the way of life. A smart display is one that is mostly out of sight.