We know this because we marked off a three-mile course with a measuring wheel and then ran it with the Amazfit Bip S and three other GPS- and HR-enabled devices: the Garmin Forerunner 735XT, the Samsung Galaxy Watch Active, and the Fitbit Charge 4. We used a Wahoo Tickr X heart-rate monitor connected to a Wahoo Elemnt Bolt bike computer to get an accurate HR measurement, because wrist-based monitors are sometimes less accurate. To avoid signal interference, we ran with only two devices at a time. The Amazfit Bip S doesn’t have many extra frills, but it’s reliable and accurate.