If you're serious about working out, you might find that the so-so heart rate sensor squashed into your smartwatch just doesn't cut it in terms of accuracy. That's where dedicated monitors like the Polar H9 (59.95) come in. A reliable, premium heart rate chest strap that won't break the bank, the Polar H9 promises to deliver instant heart rate readouts (due to its positioning next to the heart) alongside an accurate calorie burn, and can hold enough juice for up to 400 hours in the gym - that means its battery should last for around a year if you train for one hour per day. In-built Bluetooth and ANT+ tech make syncing the strap with your favourite gadget a doddle, while Polar Club support means you can even display your heart rate on screen with compatible devices. Looks like it really doesn't miss a beat.