Embodiments provide physiological measurement systems, devices and methods for continuous health and fitness monitoring. A wearable strap may detect reflected light from a user's skin, where data corresponding to the reflected light is used to automatically and continually determine a heart rate of the user. The wearable strap may include a multi-chip module having two or more electronic circuit boards with electrical connections between the circuit boards. The circuit boards may be vertically stacked or horizontally displaced within the wearable strap.
