IPhone – Meditation timer that reports mindful minutes to the Health app

It depends on your iPhone model. The iPhone 5S and later is equipped with a motion co-processor, such as the M7 in the 5S or the M8 in the iPhone 6 and iPhone 6 Plus. You can give Health permission to read data from the motion co-processor.

Also, any data from your Apple Watch (if you own one) is stored in Health. So heart rate, steps taken, walking + running distance, active calories, etc. are counted automatically.

Additionally, 3rd-party apps can use Health to log any appropriate info about your health and activity into the app, such as Nike Running or an app that can detect your pulse using the camera in your iPhone.

You can also log data into Heath and modify data yourself within the app.

I've used several apps and you do need to pay attention to which apps read from health app and which write to it.

In practice, it's pretty easy to take a screen shot of the Show All Data screen from within the Health app for Walking and Running Distance for example. Then operate the apps and enter an exercise period and repeat the screen shot after the workout is complete.

You will want to examine the hour surrounding a 5k run, for example, to be sure that your phone and watch alone are not "double dipping" if you have both on you when you run. Adding a third party app in addition to the settings you may have enabled on iOS and watchOS could triple the data.

Also, be aware that code can change so even if your app isn't duplicating data now, you'll want to sanity check things periodically in case the developer of the app changes how it reads and writes to the health database.

It's easy to go in and clean up a day's worth of double counted data, but you'll likely need an automated tool if you find out weeks or months of data isn't counted the way you prefer.