The new era of “smart health” has begun as a result of advances in advanced technology, revolutionizing patient and medical staff healthcare procedures both inside and outside of hospitals. Patients can now gather thorough health data utilizing cellphones and wearable technology, independent of their geographic location or time zone. However, present tactics for smart-health devices tend to focus on the smartness of the technology itself and on controlling a specific disease or condition. The use of this patient-generated data holds great promise for future healthcare breakthroughs in many ways. This chapter focuses on the Human Activity Tracking via Machine Learning Methods in a Smart Healthcare Informatics in which Legal Challenges, Security Issues, Opportunities and Applications towards Smart Monitoring and Diagnosis Technologies.