Ebay's smartwatch app is not a scaled down smartphone app. Don't expect to search and browse the marketplace. Instead, the device syncs with the Galaxy Note III, and only pulls features and information that fit the context of the smartwatch -- push notifications, bid and sale management. (If like me you've ever been sniped in an auction because you missed the ending-soon notification whilst your phone was buried deep inside your purse (#firstworldgirlproblems), you'll flip your wrist over this utility.)
Are smartwatch apps relevant to every ecommerce site?
For auction sites, daily deal, private sale and similar businesses, time matters, and a better push notification adds value. Not all ecommerce sites need such immediacy when all that can be delivered to a smartwatch interface and more can be accessed through a good mobile site or app. Not to mention, the smartwatch is an even more up-close-and-personal screen than the smartphone -- and tolerance for commercial push even less.
Notifications are not the only native property of Galaxy Gear - photo, GPS and voice input can also be leveraged in the experience.
The question shouldn't be how are you going to replicate your storefront to every new device, rather what pieces of your commerce platform do you want to use in your [instert device here] experience. What makes sense given the design and utility constraints of the device and its platform? What activities does the customer use the device for, and what interactions with your content and commerce enrich his or her life?
Responsive design vs. native monetization
When it comes to smart, wearable devices -- wether they be eyewear, wrist gear, headband, belt or ear muffs (hey, why not?) -- it's not a matter of being responsive, which merely delivers your www site to a small screen. It's about native monetization, and pulling the content and commerce capabilities required to deliver an experience that is contextually relevant to that device.
Branded utility apps (preferably commerce-enabled) may also do well on the watch. Vivino's app uses image recognition to match photos of wine taken through Galaxy Gear to wines (yes, Shazam for wine).
Big brands like Ebay can afford to innovate on experimental platforms that start with zero users. But most of us need a business case to support investment in new touchpoints.