Hand-held and Watch ECGs require you to sit still and hold the device with both hands, so they cannot be used during exercise. They also suffer from poor data quality, because the ECG is being acquired from the finger or wrist, instead of the chest. Further, they typically record only 30-60 second segments of ECG, and do not allow for long continuous recordings like the Frontier X.
The Frontier X was designed to get continuous ECG data at the best quality while on the move in any environment. The chest-worn design keeps your hands free for sport, and is tightly fastened to ensure good data quality during motion. By collecting the ECG from the skin just over the heart, the Frontier X can pick up minute electrical changes that may be lost if the ECG is picked up from points further away, like the arm, wrist or fingertips.
Its sturdy waterproof design also gives you the ability to use it in outdoor settings, and even record your ECG while swimming.