The number of mHealth devices and apps is growing continuously, and there is now a plethora of devices available to support health and wellbeing in health care as well as self-care settings. Devices and systems of this kind are increasingly interconnected through various forms of APIs (application programming interface), such as the Apple HealthKit and Google Fit, through which they become part of a larger ecosystem that allows for increased connectivity along with regulated and limited uses of data types. These backstage parts of mHealth and their behind-the scenes decisions are essential to take into account in order to understand what devices and systems of this kind could possibly do, and to what extent they allow for tinkering and everyday improvisation. It is uncommon that research in digital health engages with and question how these invisible backstage layers of control build on certain assumptions and how their design, marketing, and imagined functionality are underpinned by certain understandings of bodies, health, and wellbeing. Drawing on a literature review as well as critical readings of the Apple HealthKit API, this paper engages with how digital infrastructures of this kind could possibly be designed to address the complex nature of health and wellbeing.