Polar H10 Bluetooth Heart Rate Sensor for $67.49 @ B&H photo.
Normally $89.95 (regular price at Amazon, Best Buy, REI, etc), but $67.49
after clipping a 25% off coupon (see product page for the coupon). You can also order it from Polar's website with the 25% off coupon, but they charge sales tax. The promo expires today.
H10 is highly rated among runners and cyclists, and it's a great improvement over H7 for many types of workouts, as long as you don't mind using a chest strap HR sensor. You can pair it with Apple Watch, Garmin or any other wearable of your choice. as well as with your phone if you don't want to deal with wearables. It also works great with gym equipment for inputting your HR. If you have optical heart rate sensor on your watch, this will work in combination and provide more accurate reading if needed.