@incendio : it's not the openess of the app that platform owners question about; they want app from recognized entities only. That means government bodies, acknowledged research institutions, etc.
Weeks ago I prepared a prototype for a mass screening app based on an official document sent to doctors in order to conduct phone interviews. The general idea was that people autonomously collected their health status infos, sending them anonymously to a server where doctors could extract those more suspect cases and signal back to those people to contact a medical center for further analysis.