Hi Rob, You do not have to carry a smart watch or phone for the ECG to record. You can just wear the device and start a recording by double pressing the red button, and stop it with a second double press at the end of the workout/game. The data will be captured on the device and can be downloaded and synced by connecting to your mobile app at a later point of time as per your convenience. https://support.fourthfrontier.com/article/9-syncing-data-from-the-frontier-x-to-the-cloud