Energy expenditure calculation and/or generating breathing guidance utilizing wearable device

A method for utilizing real-time sensor data to guide breathing, the method comprising:

• receiving biometric sensor data about a user wearing a wearable device;
• selecting an output based on the sensor data for guiding a breathing rate and/or a breathing depth of the user;
• sending the selected output to an output subsystem selected from the group consisting of an output subsystem of the wearable device and an output subsystem of a host;
• and
• selecting a different output in response to detecting a change in the biometric sensor data.

A system, comprising:

• a processor;
• and
• logic integrated with the processor, executable by the processor, or integrated with and executable by the processor, the logic being configured to:
• receive biometric sensor data about a user wearing a wearable device;
• select an output based on the sensor data for guiding a breathing rate and/or a breathing depth of the user;
• send the selected output to an output subsystem selected from the group consisting of an output subsystem of the wearable device and an output subsystem of a host;
• and
• select a different output in response to detecting a change in the biometric sensor data.