Interconnect Devices
Consider a direct connection with other devices.

“Link devices, data, state and interactions”
Smartwatch App Design Guideline
"Share", "connect" and "link" have become verbs of mandatory use in day to day conversations. It is hard to imagine any online activity without the possibility of sharing information.
Thus, in wearable apps creation, one of the main aspects to consider is the capability of the devices and the data to be linked. As in web interactions, connections have become a must for apps.
This implies, on behalf of the devices, that one should be able to detect other, that the uses and functionalities must be equally satisfying in all devices, and that, if a state or status changes in one of them, it should be reflected on the other.
But not only devices can and should be linked to each other. Data, the inner world of a wearable, must be placed at hand and be available so that other apps can access and transform it into another kind of interaction: a global experience.
Consider a direct connection with other devices.
Expose and consume data to an accessible and common repository that can be accessible to all related apps.
State changes in data and situations on one device should be reflected seamlessly on others.
Devices are not isolated pieces of technologies.
New devices emerge and new data will be available. Think and design for the upcoming and not just for the current.
The app saves the user's running or work out data and shares it with other programs that are monitoring daily exercise and health conditions.
An app connects to a smart bracelet to complement the information of the watch to be able to monitor stress, cardiac rhythm, hydration levels and calorie intake.
A glucose level smartpatch is designed to connect with the cellphone and smartwatch, but the app does not share the data with other health apps.