There are 2 basic types of heart rate monitor watches: watches that come with a chest strap, and the newer strapless watches.
Those that come with a chest strap are usually more expensive, but more accurate. The chest strap is strapped to the skin of the chest during exercise, and device contacts the skin through moistened electrodes and picks up the electrical signals from the heart, exactly the way a hospital ECG machine does. The chest strap wirelessly transmits the heart beat information to your watch, so you get a real-time reading of your heart rate. The strapless watches are cheaper, but are less accurate. The strapless watches usually come with 2 special buttons on the watch face (although some have those buttons on the side like a regular watch). To measure the heart rate, you must stop exercising, push the two buttons with your fingers, and wait anywhere from 10 to 30 seconds. Some strapless watches try and pick up electrical signals from the heart through your fingers; these tend to be wildly inaccurate. Other strapless watches shine a beam of light through your fingers to pick up blood flow through arteries, and hence calculate the pulse rate, the same way a hospital pulse oximeter functions (the litter gadget that is strapped to your finger). Either way, you typically need to stop exercising and hold the buttons so that the device can get an accurate read and not be jostled, and for a truly accurate read, you need a long sampling time of 30 seconds to 1 minute, which is more than what most people are willing to wait, so manufacturers typically cut down the sampling time at the expense of accuracy. So basically, a chest strap monitor is much more accurate and hassle-free, whereas a strapless HR monitor watch is less accurate, but may be enough for casual use or if your exercise has natural break points allowing you to stop and take your HR.
HRM watches nowadays also come with a variety of accessories, both software and hardware. Almost all watches now come with a calorie reading which approximates the calories burnt from your heart rate. This is useful if you are trying to lose weight. Some HRM watches, especially the pricier ones, is basically a little personal fitness trainer, and come with software that can recommend target heart rates and exercise regimes, and then monitor whether you’re sticking to that plan. These tend to be rather difficult to program and use, and such functions are widely ignored by owners. On the hardware side, the most common accessories are a foot pod pedometer to measure the number of steps you take, as well as a GPS receiver to measure your position and speed. Both of these accessories are very popular with runners and cyclists, although they may be only for the serious athlete. Certainly, the addition of a GPS receiver will seriously up the price tag on the HR monitor such as Garmin Forerunner series GPS capable HRM sports watches.
So in conclusion, there are a variety of heart rate monitor watches that you can choose from, at various price points and with different features, so that you can choose one with a set of features you want. In my coming articles, I will review a few of the most popular models of HR monitor watches.