We recommend downloading the Active for Good app to use your phone as your tracker. It connects to your phone's health data app (iOS Apple Healthkit, or Android Google Fit), so you can also enable 3rd party apps to be data sources on your phone's health app & that will then push to your challenge dashboard! See here for instructions on how to do that (iOS/Android).
Fitbit and Garmin devices are the only other devices we connect to directly. To add one of these trackers, see how to add a tracker here.