The only difference is that, the treadmill heart rate monitor is attached on the treadmill and could not be carried around wherever you want. Many treadmills today has a built in heart rate monitor. The function conforms to the general use of a heart rate monitor. It keeps you on tract with your heart rate while doing your exercise on the treadmill. And when you do such activities, there is a need for a large display. Large display would enable you to read easily in arm s length your heart rate without the need of stopping for few seconds. Along with the display, the right heart rate monitor should have big buttons. This would give you the ease of pushing your heart rate monitor with your finger while you are moving. And with the length Nike has been in the market offering top quality sportswear such as shoes, shirts, and pants, and equipments such as bags, different kinds of sports balls, and others from different sports arena, it is just right that the company would also give its consumers the right fitness companion. And with its size, you can have the convenience of treating it more as an accessory than an exercise tool. 4. Mobility. A wristwatch heart rate monitor would only have to be worn on the wrist without interfering with the exercise. It is light, compact, and stylish which would make it more wearable. Wearing a wristwatch heart rate monitor would still give you the freedom to move in ways you want to. She realized that the best way to have her weight back was to be conscious about the food she eats and the level of exercise she would take. Actually, Liz realized this after she gave birth to her third child. While she aimed to achieve this, the market had yet to have the suitable product that would answer this. Expanded features: While it is advisable for beginners to get the basic heart rate monitor and work from there, others might be very eager to try higher-end heart rate monitors with calorie counters, built-in training program, and built-in trainer-like features that would guide user throughout the whole training, the choice is still up to you.