Fitbit - companion app for popular wearable fitness trackers | AndroidTapp. Hey, fitness fanatics! Do I have an app for you! If you own a device that tracks every one of your fitness activities, and you have a perverse need to see, on a screen, the progress you are making towards the final end of life that we all are marching towards, you need Fitbit, which is an app that will connect to your device and send the results to your phone. What is this national obsession with measuring life? How about an app that helps in just living it? I think I will go read a digital magazine now, while my SmartWatch gently vibrates when I get a phone call or email.