There are a few things to watch out for when buying a heart rate monitor. Firstly, it is important to find a monitor that fits snugly around your chest. Otherwise, you might not get accurate readings. It might also be uncomfortable. Secondly, make sure all the features you want are present. Features like alarms and timers are very useful and should be present in the best heart rate monitor. Thirdly, ask yourself how easy the heart rate monitor is to use. The display and instructions should be clear, and buttons should be easy to press. After everything else, consider whether the product is within your budget.