Know your zone with Forerunner 225 — the first Garmin GPS running watch with wrist-based heart rate. Now you have the option to run without a heart rate strap because this watch has a built-in sensor using Mio Heart Rate Technology that measures heart rate at the wrist.In addition to using GPS to calculate distance and pace, the 225 has a built-in accelerometer. This allows it to capture distance and pace data when you’re running on an indoor track or treadmill, with no need for a separate foot pod accessory. It even doubles as an activity tracker¹, counting the steps and calories you burn all day.