Nowadays, there are a lot of new mobile devices that have the potential to assist healthcare professionals when working and help to increase the well-being of the people. These devices comprise the Internet of Medical Things, but it is generally difficult for healthcare institutions to meet compliance of their systems with new medical solutions efficiently. A technology that promises the sharing of data in a trust-less scenario is the Distributed Ledger Technology through its properties of decentralization, immutability, and transparency. The Blockchain and the Internet of Medical Things can be considered as at an early stage, and the implementations successfully applying the technology are not so many. Some aspects covered by these implementations are data sharing, interoperability of systems, security of devices, the opportunity of data monetization and data ownership that will be the focus of this review. This work aims at giving an overview of the current state-of-the-art of the Blockchain-based systems for the Internet of Medical Things, specifically addressing the challenges of reaching user-centricity for these combined systems, and thus highlighting the potential future directions to follow for full ownership of data by users.

With the dramatic increase of the Internet of Medical Things devices, self and remote health data monitoring is consistently receiving more attention. However, medical devices are usually challenging to deploy due to privacy regulations, and they generally leverage a centralized third party. Enabling data sharing would enhance new medical studies, formulate new treatments, and deliver new digital health technologies. Solving the issue will have a triple impact: we will handle sensitive information easily, contribute to international medical advancements, and enable personalized care. A possible solution is to exploit decentralization distributing privacy concerns directly to users. Solutions enabling this vision are closely linked to Distributed Ledger Technologies. Through its characteristics of immutability and transparency, this technology would allow privacy-compliant solutions in contexts where privacy is the first need. This paper envisions the InterPlanetary Health Layer and related real-world implementations in the Internet of Medical Things domain. The main idea of the proposed solution is to handle sensitive data by preserving privacy and guaranteeing data availability. Specifically, users can build their private network, collaboratively authorize operations among their data and manage their privacy conditions without relying on a third party. The results of several stress tests conducted on a real case study confirmed the feasibility of the proposed solution, which shows good scalability and a modest impact on the application performance measured during the decentralized data access.