There are literally thousands of health related mobile apps available for download on the main Play Stores, as well as from a few curated libraries that were set up to provide some measure of quality control.
Mobile-based apps all use the built-in sensor devices available, usually the camera or the microphone, and sometimes the accelorometer. However, the vast differences in specs between each mobile model make these systems somewhat unreliable.
Most of these apps would be more effective with a purpose-designed external sensor performing the actual measurements, with the mobile device handling the analysis and cloud storage. (As with an external step or movement tracker worn on a wrist.)
