With the abundance smartphones and their ability to connect directly to many local devices, smartphones have seen usage as aggregators for much of a persons data. While this data is useful for the owners to have and view locally, there are many scenarios where the sharing of this data can be a significant advantage to the owner. The scenario closely examined in the following is the transmission of a diabetic's physiological data to their doctor. Starting with this example, use cases and requirements are created for a generic sharing and synchronization system. Using these requirements, several existing solutions and theoretical approaches are evaluated. This evaluation found that existing solutions either do not offer enough granularity in sharing their data, are not generic enough or are not designed to work with a mobile device as a data source. Therefore a solution is designed to allow users to share their data in a fine granularity with any number of users that requires little overhead. To create the fine granularity, the solution is inspired by existing access control methods that return only those parts of the document that a recipient is granted access to. By integrating the sharing information into the document with use of shareables, the document can be transformed into a document that contains only the data that the recipient is allowed to see. This allows for a difference to be found between two version of a document on different devices. Furthermore, any instance holding the entire document can perform the same transformation and act as a redistributor of the document. As a proof of concept, the solution is implemented so that when it compares the two documents it synchronizes only the information added to the document, not information removed or modified. The implementation is evaluated according to the requirements previously created and found to meet them. Furthermore the implementation is evaluated in terms of how much data is transmitted and the run-time of a synchronization. While in both cases there is room for improvement, augmentations to the simplistic algorithm for finding the delta are presented to reduce both the data transmitted and run-times. The evaluation shows that while more work is needed, the concept itself is sound.