Wearables are not all smartwatches.
Wearables are, currently, not very good at input. Not just me, but anyone who writes about their serious love of anything (mostly smartwatches) says the game changer is near-ambient notifications.
Also: gathering general info, such as fitness trackers. But that's sensor extension, not deliberate user input.
Future tech is full of wearables http://www.technovelgy.com/ct/SrchRes.asp and there are already (mostly experimental or very, very specialized) smart clothes.
Principles of Wearable Design
These are not solid, but I am using them on the wearable (and sometimes other IoT) products I have worked on. See below for "open questions" that would help clarify:
Glanceable
Devices with visual output must present useful information instantly, so users can glance quickly. Let's define a glance as snapping their eyes to the device and back to another task in under 125 ms.
Conspicuous
To the user. Not generally. Basically, I mean that it needs to grab the wearer's attention when there is an alert to be given.
Covert
The other side of this is that what alerts it does give (and the general design) should not give away it's intent or information, draw attention to the user, or distract from other, real world interactions.
Filterable
A key point of a wearable is being aware of a large set of the digital interactions occurring, without having to stop and check your phone, tablet or computer. Notices must be presented in such a way they can easily and immediately be understood and a decision made to disregard/dismiss or take action.
Actionable
The wearable should never do anything that is a dead end. More information should be available, whether on the wearable or by working in coordination with a connected device, such as "read on phone." Informing the user is not enough; an action on the wearable should coordinate with the handset and pull up the information directly.
Open Questions
I would love to research these. I have ideas how, but have yet to get anyone to help me.
- How often they are glanced at.
- How quickly (and frequently... success rate) after a notice they are glanced at.
- How often that results in further actions.
- How often used for ambient info. Time, weather, etc. that is always displayed.
- Issues with not-always-on devices like Apple Watch.