Most current smartwatches, such as the Pebble and the Galaxy Gear, serve as notification hubs for whatever smartphone is paired to them, but this limitation is something several Kickstarter projects have sought to change by effectively turning smartwatches into phones themselves. This approach doesn't address how ludicrous it is to peck out words on such a tiny screen, but Minuum, the Android keyboard that fits the entire alphabet into a single row, could just be the ideal solution. The team has released a video showing the magic in action.
On phones, I find using Minuum to be more hassle than it's worth, especially when the time comes to type out passwords (even with its ability to pull out a full keyboard as needed). Yet I can see a tangible benefit to sticking it on a smartwatch, even if, ultimately, you would probably still be much better off just pulling out your phone.