Lark is a great free app that makes use of Health app using the HealthKit API. Lark uses the lower power sensors in the iPhone 5s, iPhone 6, and iPhone 6 Plus to track your activity, eating and sleep data without draining your battery. No extra sensors are required, but it does require you to have your iPhone on you every time you move to collect data. Something that I am not too good at.
You can authorize Lark to share its data with Health app. This will allow you to use Health app’s simple and informative graphs and charts to analyze the health and fitness data gathered by Lark.