Soft, comfortable, and able to run just about forever, Garmin's HRM-Tri heart rate monitor is a key piece of the arsenal of every triathlete or high-level endurance athlete. It's perfect for dry land activities and wetsuit swims, though it isn't recommended when you're swimming without a wetsuit. Garmin claims that the included battery will last for ten months if you use it for an hour every day, and the HRM-TRi transmits wirelessly to Garmin Epix, Fenix 3, and Forerunner 920XT devices for easy performance analysis.