The key to an effective cardio workout is how and when you elevate your heart rate. A handy heart rate monitor allows you to easily check when you're entering aerobic, anaerobic and recovery zones throughout your workout. Heart rate monitors can also show you how your endurance and cardio fitness is improving as you continue on with your workout regimen. If you enjoy walking, jogging or running, a combination stopwatch and heart rate monitor may be your best bet. If you lead an especially active lifestyle, it can be helpful to know how much "ground" you're covering throughout your busy day. Why not try a pedometer to measure your countless steps and mileage? Shop top quality fitness monitors and watches from great brands like Timex, Polar, Casio and more.