The designers of the Pebble watch realized that a mobile phone is more useful if you don’t have to take it out of your pocket.:

Eric Migicovsky didn’t really want a “wearable computer.” When he first conceived of what would become the Pebble smart watch five years ago, as an industrial-design student at Delft University of Technology in the Nether­lands, he just wanted a way to use his smartphone without crashing his bicycle. “I thought of creating a watch that could grab information from my phone,” the 26-year-old Canadian says. “I ended up building a prototype in my dorm room.”