Several wearable gadgets are now available from tracking fitness to medical cond

Several wearable gadgets are now available from tracking fitness to medical conditions monitoring and controlling. These devices (called sensors) interconnect themselves and the main systems wirelessly. In your opinion:
How useful are these devices for monitoring daily health activities: physical, blood glucose, blood pressure, pulse rate?
How secure is the data transmitted by them wirelessly?
What is their role in healthcare fitness through tracking health activities: physical, blood glucose, blood pressure, pulse rate?
How these technologies help in monitoring and controlling chronic medical conditions: diabetes and hypertension (high blood pressure)?