There are very few things more accurate at tracking your workout progress than a heart rate monitor. They allow you to stay within the optimal heart rate range for your various fitness goals, while providing an essential feedback that makes the process more motivating for many people. The Fitness HR device tracks your bpm, while feeding that info to your smartphone through Bluetooth. It’s normally $80, but today’s deal sees the price drop to $40. Paired with the iMaze fitness app, you’ll be on the road to a rock solid physique in no time.