"Pedometer+Walk weight loss" uses your iPhone’s built-in-pedometer to track your steps. It records the number of steps you have walked and displays them again along with the number of calories that you have burned, distance, walking time.

This app calculate calories depending upon weight & distance and add them to the HealthKit store.

It is easy to use. Once you gave all permission & all you have to do is hold your smartphone as you always do and walk.
Of course, it will continue to automatically record your steps even if you put it in your pocket or bag. This happens because pedometer calculates steps based on vibration pattern.

 It quantifies metrics such as steps taken, calories burned,  and distance covered, and rewards you once you reach your goals.

HealthKit It uses permission for getting app communicate with the HealthKit store to access and share this data within our app.
App uses Health-Kit to import your calorie related data from app to Health-Kit.