Abstract: The invention provides a monitoring device that features: 1) a cardiac sensor component with at least one light-emitting diode and a photodetector; 2) a pedometer component with at least one motion-sensing component (e.g., an accelerometer); and 3) a wireless component with a wireless interface that communicates with an external weight scale. The device also features a microprocessor in electrical communication with the cardiac sensor, pedometer, and wireless components and configured to analyze: 1) a signal from the cardiac sensor component to generate heart rate information; 2) a signal from the pedometer component to generate exercise information; 3) heart rate and exercise information to generate calorie information; and 4) a signal from the external weight scale to calculate weight information (e.g., weight and percent body fat).