The Roadster showed Tesla Motors can design a top-notch electric drivetrain. The Model S showed it can design a gorgeous car. Building the S is another story, of course, so now the Silicon Valley upstart wants to show it knows a little something about

LAS VEGAS — Nike launched its successful Nike+ fitness software just four years ago, but nearly 4 million users have turned it into the most popular and widely available run-tracking UI ever. And just four months ago, Nike enabled GPS tracking in a completely