I'm thinking about picking up one of the new Nano's strictly for running/working out. I don't want to use my phone on the chance that I drop it/smash it with a weight. I have a 4th gen iPod Touch that I've been using for working out/running, but it's become extremely laggy (esp. when compared to my iPhone). All I need the Nano for is music/podcasts, so other added apps and features don't matter to me. Now for the Nike+ app... How does it track your runs and progress without a GPS signal? I'm familiar with using similar phone apps, such as Endomondo, when running which give a nice tracking of where I'm running, how fast, average mile, etc. Is the Nike+ app accurate on the new Nano in terms tracking your runs, mile times, calorie burns, etc?