Because of the cross-device integration, the watches can do many of the same things as other mobile apps, as well as hand off to other devices. A lot of the notifications offered are similar to Google's Cards.
The Moto 360, scheduled to ship this summer, seemed to be one of the more attractive watches shown off by Google.
Google's application programming interface allows for both round or square watches; Motorola is thus far the only one offering a round one. Also, skeumorphism for the win!
The food-ordering app was a big hit.
You can't fit a lot of information on one of these watch faces, as you'd expect.
LG's watch seems closest to shipping, though it's not the most attractive or (in my opinion) really suited for women's wrists.
The LG G seems awfully large.
This interface will have notifications and status reports similar to Android phones.
The LG G also offers a blend of the analog and the digital; a notification about your flight on the bottom, and voice commands.
An app can interface with Lyft.
Unsurprisingly, you'll be able to look stuff up via Google search.
If you're in the middle of something important, you can send yourself a reminder (to appear on another system) to check on your email later.
This is one of the applications I think makes sense for a watch, if you can set it to pop up automatically with no input. That way, you can see your plane status while your hands are busy schlepping luggage.
Your watch can tell you whether or not you need to rush.
Though we didn't get to see Samsung Gear -- Google only announced the partnership -- as with the other watches there will be vibration notifications, music app controls, voice reminders, and customized phone-call dismissing.