The on-demand digital healthcare ecosystem is on the near horizon. It has the potential to extract a wealth of information from “big data” collected at the population level, to enhance preventive and precision medicine at the patient level. This may improve efficiency and quality while decreasing cost of healthcare delivered by professionals. However, there are still security and privacy issues that need to be addressed before algorithms, data, and models can be mobilized safely at scale. In this paper we discuss how distributed ledger technologies can play a key role in advancing electronic health, by ensuring authenticity and integrity of data generated by wearable and embedded devices. We demonstrate how the Masked Authenticated Messaging extension module of the IOTA protocol can be used to securely share, store, and retrieve encrypted activity data using a tamper-proof distributed ledger.