I did a few test runs with my Apple Watch while paired to my iPhone and the current pace displayed on my watch seems to be pretty off. Because I need the iPhone for its GPS chip I carried it in my waist pack. But does the iPhone need good line of sight with the sky for accurate GPS readings? Or should it be able to get a good GPS reading while tucked into a waist pack? I'm running in area where my Garmin never had a problem picking up GPS. And interestingly, the average pace displayed at the end of my runs with Apple Watch seem pretty accurate, it's only the current pace that it can't seem to get right.