I'm reading several articles and Apple's documents regarding Apple Watch and WatchKit development. It looks like third-party apps for Apple Watch like Strava and Runtastic will need you to also carry your iPhone while doing exercise to take and show data (as described in App Store Apps), but I don't find if the built-in apps (Activity and Workout) will also need it. It looks a bit uncomfortable having to carry your iPhone while running to be able to see your heart rate, speed and so on in the watch...
Regarding the data measured by the heart rate sensor and accelerometer integrated in the Apple Watch: is there an API that makes them accessible to third-parties developers?
And how is data mesaured by those sensors handled by the watch: is it directly sent to the paired iPhone as it is measured? It is temporarily and locally persisted in the watch until it is possible to send it to the iPhone? Is HealthKit available for WatchKit apps to handle such information?
Thanks in advance
I played with the Apple Watch at the Apple Watch lab.
The sensors and accelerometer are not accessible to devs.
You can go running without your phone and when you get home the heart rate data will 'eventually' be sent to Health on your phone, from which you can query data for your app. Any heart rate or sensor data saved on the Apple Watch cache is not accessible to dev.