Health-related mobile applications (apps) have been shown to improve the quality of health and patient care. Their use in clinical and health-related environments is becoming more considerable. The number of health-related apps available for download has considerably increased, while the regulatory position of this new industry is not well known. Despite this lack of regulation, measuring the usability score of these apps is not difficult. We compared two samples of twenty health-related applications each. One of the samples contained the apps with top-rated usability scores, and the other contained the apps with lowest-rated usability scores. We found that a good usability score correlates with a better medical reliability of the app's content (p<0.005). In the period in which a valid regulation is still lacking, calculation and attribution of usability scores to mobile applications could be used to identify apps with better medical quality. However, the usability score method ought to be rigorous and should not be rounded off with a simple five stars rating (as is the case in the classic app stores).