These days your phone holds more than just digits. With all those fitness apps, from Map My Run to iTreadmill, it's almost like having a trainer in your pocket. Then there are the emergency situations that could arise if you're out on a trail or have biked miles from home. For many on-the-go gadget gals, the phone doubles as an MP3 player — another reason to work out with your phone. I admit, I rarely run with my phone, but always bike with it. What about you?