The Moov HR Burn chest strap with accompanying iPhone app. Share on Facebook Here, I put the gadgets to the test. I focused mostly on devices that are for running or indoor bodyweight exercises, so they’re applicable to a wide audience of people. Many of these products contained a heart rate sensor, which worked in one of two ways. Chest straps are considered the gold standard because, using electrodes, they detect your pulse at the source — electrical signals that instruct your heart to contract. An increasingly popular alternative is optical heart rate sensors, which shine a light into your capillaries to observe your blood flow, most commonly at your wrist. These tend to be less accurate than chest straps because things like movement can throw off the readings. I tested all devices with an optical sensor against the Wahoo TICKR X ($80) and Polar H10 ($90) chest straps. The Moov HR Burn chest strap with accompanying iPhone app. The Moov HR Burn is a chest strap that pairs wirelessly with a free app that talks to you, guiding you in real time through four different indoor-exercise classes, as well as outdoor runs and indoor cycling workouts. Moov’s coach reads your heart rate to check if you’re working hard enough. When you are, “she” congratulates you (“You’re doing great!”), and when you aren’t, she cheerfully scolds you (“Time to push it!”). It surprised me how much these quips kept me going, even when I thought my thighs were going to fall off. The outdoor runs and indoor cycling workouts, which alternate between all-out sprints and easy recoveries, start at 18 minutes. To get a better sense of how the product works, watch the video above, or listen to our episode of the Decrypted podcast, in which you’ll hear my boss Brad valiantly trying the Moov HR Burn for the first time.