Take your training to the next level with Garmin's Heart Rate Monitor Chest Strap. It's compatible with many of their GPS units and wirelessly gives you an accurate read out of your heart rate. Plus, it features ANT+ technology for seamless, interference-free data transferring. The front part of the strap contains the heart rate module and is made of flexible plastic while soft fabric goes around the back and is adjustable to your size.
ANT+ is a wireless technology that allows your monitoring device to seamlessly communicate with other ANT+ products such as speed sensors, heart rate monitors, power meters, and foot pods that track running/walking progress.