Wahoo Fitness TICKR HR Monitor Armband

A great alternative to a chest-strap monitor, the TICKR HR Monitor comes with two different-size straps so you can adjust for fit and comfort. It measures heart rate and calorie burn during exercise. The armband has a water-resistant IPX7 rating and a 30-hour runtime.

It also connects via Bluetooth so you can pair it with Strava, Zwift, a Nike Run account, and more.