This document discusses substitutable medical apps and reusable technologies. It describes how a blood test app was overhauled by one developer in one week using an open API, documentation, and example data. The app integrated data authentication and user interfaces. The document advocates for open formats and unrestricted, realistic example data to promote innovation. It notes that while CCR and CCD formats are licensed for temporary storage and single printing, a blog later highlighted a lack of freely available examples. Overall innovation in healthcare apps requires open platforms, documentation, and access to sample clinical data.