~ Written by Pravin Carvalho, Principal Engineer
At the most basic level, both Apple HealthKit and Google Fit provide for the aggregation of health data from numerous sources and presents the end user a single holistic view of the user’s health information. These platforms also serve another very important purpose of enabling data interoperability by standardizing the syntax (how the data is structured) and semantics (what the data means) of data sets associated with a specific health measurement.
Normalizing the semantics is a great benefit to the overall industry since all users of a platform agree to the same meaning of the underlying data. This is needed for doing meaningful analysis on the data. For example, even a simple word like “Sleep”, which may mean something very different to different people, will mean the same thing for all applications that use a platform that has defined the word “Sleep”. For example, sleep analysis data is stored as a categorical variable in both Apple HealthKit and Google Fit differently. In Apple HealthKit, the allowed values are “In Bed”, “Asleep”, “Awake” while in Google Fit, the allowed values are “Sleep”, “Awake”, “Light Sleep”, “Deep Sleep”, “REM Sleep”. When implementing either platform, extreme care should be taken in making sure that the data model (syntax and semantics) is followed to prevent incorrect information from being used by the end user which may also potentially be harmful.
While Apple and Google created these platforms to help address interoperability of health data within their operating systems, using one or the other does not necessarily force you into an Apple or Google only solution. For a cross platform solution needing the same user experience across both iOS and Android, we successfully implemented a hybrid approach using the supplied platforms augmented by custom code.
HealthKit can be thought of as a central repository for storing health information in iOS which can be viewed using the Apple Health app. HealthKit allows apps to securely read and write health data while respecting the user’s privacy. The user is also provided with granular control over uses of their data such as which apps can read or write which data. For example, a fitness app can be authorized to write certain fitness related data to HealthKit while another healthcare management app can be authorized to read the data from HealthKit to provide suggestions to the user. The Health App also provides the ability to visualize, add, or edit data stored in HealthKit. It should be noted that Apple does not provide any APIs to access or store HealthKit data through a cloud service. The data used by HealthKit resides only on the user’s device.
When considering HealthKit, one should review the latest Apple App Store guidelines for specific restrictions. For example the Sept, 2018 Apple’s App Store review guidelines state that apps are not permitted to use data in HealthKit for marketing, advertising or use-based data mining other than in cases for improving the health management or research and then only with the permission of the user.
Google Fit addresses more than data interoperability and looks at the workflow of sensing, collecting, and tracking data. Similar to Apple HealthKit, Google Fit also has a robust security and privacy model. The data is presented to the user using the Google Fit app which is similar in purpose to the Apple Health app, providing the user similar granular control of uses of the data. The broader scope does not mean however, that Google Fit is applicable for all use cases. According to the latest Google Fit Terms and Conditions (Sept, 2018), “Google does not intend Google Fit to be a medical device. You may not use Google Fit in connection with any product or service that may qualify as a medical device pursuant to Section 201(h) of the Federal Food Drug & Cosmetic (FD&C) Act.” In positioning its platform, Google seems to be addressing more personal fitness monitoring as opposed to all aspects of personal health or illness monitoring. While the Google Fit API supports the storage of a number of health measurements (e.g. oxygen saturation, menstrual flow), the Google Fit app currently only displays activity, weight, and blood pressure. It should be noted however that the Google Fit API supports limited medical data types. For example, it presently supports blood glucose and body temperature but not insulin delivery. Unlike the Apple Health app, the Google Fit app does not allow the user to edit individual data points. However, the user may choose to delete all data of a particular type.
In contrast to Apple HealthKit, Google Fit provides several mechanisms to extend the use of the data beyond the user’s device, all natively within the Google Fit platform. For example, Google Fit provides a communication mechanism which allows developers to use Google Fit APIs to send and retrieve data from a device or app to a central cloud based repository called the Google Fitness Store. Transmitting to a cloud service is also possible using Apple HealthKit but it would require an app to read the data from Apple HealthKit and transmit this information to the cloud service. Note that this must still comply with Apple App Guidelines as noted previously. Another communication mechanism offered by Google is a Google Fit REST API which enables authenticated access to store and retrieve data from sources other than Android devices such as iOS devices, and web or PC applications. Using the REST API, applications can read and write to data stored on the Google Fitness Store cloud service. With regards to assisting sensing on Android, the Google Fit API also provides support for collecting data from Bluetooth Low Energy sensors that implement a standard protocol (GATT profile) as defined by the Bluetooth SIG. This flexibility may be needed by certain systems to implement the latest standard protocols.
How we can help
Understanding how your data will interoperate is one of many considerations when architecting and designing an optimal connected medical device solution. While platforms like Apple HealthKit and Google Fit facilitate certain aspects of a deployment, use of these platforms still needs to be a part of an overall product strategy. Jointly working with our clients, we help to develop a robust product strategy, make the right technology decisions and deliver a production ready scalable solution. Having also successfully developed applications that comply to FDA, CE and other global regulations, we can design a solution that complies with the regulatory strategy set out for your product. If you are interested in connected medical devices, contact us.
We’re excited to hear your ideas and discuss more about our development experience.